Under-Propped ?

[Marian Claire]

[[[Edit:The RPM #s in this post are no good. I found that my tach was way off. Corrected #s in a later post.]]]
I have discussed this issue with a few forum members but now that I have more info and a plan I wanted to post. The basic problem is I never reach hull speed, or even close, under power. I believe my hull speed works out to be 7.6 MPH with a 25 ft LWL. I will use MPH due to traveling on the ICW.
I did some test runs the other day and they are very similar to tests in the past in calm conditions clean prop etc.
1200 RPM 3.1 MPH
1400 " 3.5 "
1600 " 4.0 "
1800 " 4.5 "
2000 " 5.0 "
2200 " 5.5 "
2400 " 5.7 "
2600 " 6.0 "
2800 " 6.2 "
I have the 2 to 1 reduction gear and the engine showed no sign of strain or of topping out.
I have sailed faster than this so I do not think it is a hull speed issue. I just think I am under propped. The prop is 14X?.
From the #s, point of diminishing returns, and the 2000 to 2500 RPM continuous use recommendation for the A-4. I will shoot for 2200 as a cruising RPM with a few hundred more in reserve.
From what I understand you lose 100 RPM per 1" of added pitch. I can not go to a bigger diameter due to the MCs aperture. My plan is to add 2" of pitch to my existing prop no matter what pitch it turns out to be.
1. Does this sound reasonable?
2. What is the max a props pitch can be changed?
3. Extra Credit: What kind of performance improvement can I expect?
I have contacted several prop dealers and they have been helpful but none of the props they suggest are 14" and some are to large for the aperture. The smaller ones might be negatively impacted by the width of the keel just 5 or 6 inches forward of the prop. Plus the MC is a homemade boat so there are no boats to reference her to. I would like to modify and use my existing prop if possible. Thanks. Dan S/V Marian Claire

[Dave Neptune]

Dan, with a 14" prop you should be able to go up 2" or even a bit more. However do make sure that the prop has not been pitched up a bit already. Increasing pitch will move the "rake" of the prop in a positive direction, a good thing. This will put more of a load on the outside dia of the prop which is a good thing on an aparature app.
Is it a 2 or 3 blade?
Often with close and thick deadwood it is good to go to the larger diameter in a 2 blade and cut the dia down leavig the blades with a more square looking end. This will give you a 2 bladed prop you can still hide and the larger prop gives you wider blades especially out where they are "exposed:eek:" giving you far better traction.
I would also look at the load on the engine with a vac gage on the last 3 RPM settings. That can give good insight into how much to pitch or just go bigger and cut down.

Dave Neptune :cool:

[Marian Claire]

Knew I would forget something. It is a 2 blade. Thanks for the idea of cutting back a larger diameter. Will the prop shop be able to tell if the prop has been changed before? Dan S/V Marian Claire

[Ball Racing]

If it's a good shop, they will re- mark the new number on the hub over the old #, or cross out the old.(the old pitch number should still be there)
On most boats, even though they can all act different,, one inch of pitch or diameter makes around 200 rpm change.

[Dave Neptune]

Dan, std operating procedure is for the old number to be "X"'t out or ground off and the new pitch will be stamped on the hub or one of the faces of the hub. It is not uncommon to see 2~3 "X"'t out on old props.
Re the 15" dia you shold be able to find one on line ar at a use chandlery for a trade or about 30~40% of value if it is good shape. You can also get a prop for a larger shaft and use an adaptor, they work fine and it will increase the probability of finding something close. Remember on the style prop you are looking at only pitch up or buy a prop that has been pitched up. Walk away from anything else.
Don't disregard the engine load, it is easily measured by manifold vac at any specific RPM.

Dave Neptune :cool:

[Maurice]

Hi Dan,
Let's look at the boat also. Do you have the calculation formula for hull speed worked out properly. Personally, my C&C 30 has a water line is 24.6 feet (I taking this from memory) and my hull speed is 6.6 kts. When I first put the boat in the water in the spring, bottom clean with fresh paint, water tanks empty and no accumulation of junk (yet) I hit 6.2 no problem. Once I start loading her up it will be 6.0 kts under the engine....this happens as soon as I load the boat (I do put allot of "junk" on though for kids, food, games, books, toys...you name it.

Hull speed for 25 foot waterline is about 6.75 kts.

http://www.cncphotoalbum.com/technical/hullspeed/hullspeed.htm

Hope this helps you out. I think I'm using a 12/6 three blade....I can double check that as the boat is now on the hard. Direct drive.

[Marian Claire]

Mo: I believe so. I get 6.7 knots and that times 1.14 statute miles/nm is how I got the 7.6 MPH. I know using MPH is goofy on a boat but that is how the ICW is marked/measured. So bridge timing, distance to next anchorage etc is easier to figure if I know my speed/potential speed in MPH. I am sure the load I carry when cruising is a factor but I read of boats with similar LWL and higher displacement, the MC is 10000lbs, getting up to hull speed with the 2 to 1 gear. The boat was relatively light for this last test run. Water tanks empty, no extra fuel etc. I do not come close to 7.6 mph even at 2800 RPM.
I hope someone can answer #3 or tell me there is no way to know. I am not looking for miracles here but even a 10% improvement would make a big difference on a long trip or crossing to the Bahamas.
BR: Even the guys in the yard could not find markings on my prop. The other two that came with the boat are marked as you describe. I will double check my info. What I have read is 1" diam = 200 rpm and 1" pitch = 100 rpm. This seems to be mostly applied when boats are over propped and they are trying to get the rpm up. I am assuming it works in reverse?? If your #s are right I will need to back of on my plan. I want to be able to hit at least 2500 rpm as that is about 20 hp for the A-4 and I have been told I need 20 hp to get to hull speed.
Dave: I do have a 15X12 prop so your idea of cutting one down may come into play. I am researching the vac gauge issue.
What rpm/vac #s would be most helpful?
I also found one cross reference to a 14" prop. A 14X10 or 14X11 is equal to a 15X8, all two blades. A 15X 8 is one of the props suggested by Robert Hess for the A-4. So I have something to aim for.

Thanks to all. Dan S/V Marian Claire

[Marian Claire]

I have the early model manifold so I would need to drill and tap it for the vac gauge. Could I avoid that by installing the spacer/adapter sold by Moyer for using a late carb on a early manifold and connecting the gauge there? I have a spacer and that would be fairly easy. Dan S/V Marian Claire

[Marian Claire]

I think BRs pitch to RPM numbers are better than mine. I can not find the 1" pitch = 100 rpm that I used. They seem to range from 1" = 150 rpm to 1" = 225 rpm. So 1" = 200 rpm sounds good. Thanks. Dan S/V Marian Claire

[joe_db]

What happens past 2800 RPM?

[Marian Claire]

I pushed her slightly past 2800 briefly and she ran fine. In hind sight I should have run it up to WOT. I just did not think I would ever run that high in regular use so why go there. I am learning as I go. My logic was if she can handle 2800+ rpm with the existing prop. Then I could increase the pitch and even if I lost a few hundred rpm so what. I would still hit the "magic" 2000 to 2500 rpm range and hopefully have a little more speed. I am beginning to realize its not that simple. Dan S/V Marian Claire

[Dave Neptune]

Dan, I am a direct drive using the Indigo and my power curve is fine.
1800 RPM @ 10" of vac easy cruise .7~.75 GPH
2000 RPM @ 8+" of vac cruise @ just over .8 GPH
2200 RPM @ 7" of vac fast cruise @ just about 1 GPH
2400 RPM @ 4.5" of vac oh KRAP cruise @ about 1.3 GPH
WOT 0" vac @ 2600 rpm throttle arm about 1/2 way open any more throttle equals a bog because we are at close to 0"'s or effectively full throttle.
Most of us who use the Indigo are very pleased with what Tom has worked out with this prop. If you can hit around 4.5~5.5"s of vac at your max power cruise you will still have a bit of reserve and the engine will spin in a very happy manner. With your 2:1 advantage you should shoot for a 2800+ for your effective WOT. Once you reach around 4" of vac you can gain very little power by advancing the throttle. A good easy cruise at around 7" works very well for economy and not to much cylinder preassure at lower RPM's. I use the stock J-8's @ .035 gap (they last about 3 seasons and I change them out) and my engine is in good tune but very tired (it's been running for 43 years now & 26 with an EI) with low compression in the back 2. I have also leaned the mid range of my carb and use a fixed jet!
A good base of calculation for these A-4 flatheads is 2.2HP per pound of fuel per hour, this can very a bit up or down depending of fuel mix and tune.

Dave Neptune :cool:

[ArtJ]

Mo: I believe so. I get 6.7 knots and that times 1.14 statute miles/nm is how I got the 7.6 MPH. I know using MPH is goofy on a boat but that is how the ICW is marked/measured. So bridge timing, distance to next anchorage etc is easier to figure if I know my speed/potential speed in MPH. I am sure the load I carry when cruising is a factor but I read of boats with similar LWL and higher displacement, the MC is 10000lbs, getting up to hull speed with the 2 to 1 gear. The boat was relatively light for this last test run. Water tanks empty, no extra fuel etc. I do not come close to 7.6 mph even at 2800 RPM.
I hope someone can answer #3 or tell me there is no way to know. I am not looking for miracles here but even a 10% improvement would make a big difference on a long trip or crossing to the Bahamas.
BR: Even the guys in the yard could not find markings on my prop. The other two that came with the boat are marked as you describe. I will double check my info. What I have read is 1" diam = 200 rpm and 1" pitch = 100 rpm. This seems to be mostly applied when boats are over propped and they are trying to get the rpm up. I am assuming it works in reverse?? If your #s are right I will need to back of on my plan. I want to be able to hit at least 2500 rpm as that is about 20 hp for the A-4 and I have been told I need 20 hp to get to hull speed.
Dave: I do have a 15X12 prop so your idea of cutting one down may come into play. I am researching the vac gauge issue.
What rpm/vac #s would be most helpful?
I also found one cross reference to a 14" prop. A 14X10 or 14X11 is equal to a 15X8, all two blades. A 15X 8 is one of the props suggested by Robert Hess for the A-4. So I have something to aim for.

Thanks to all. Dan S/V Marian Claire

Hull speed =1.34 times (square root LLWL) which is 1.34 x 5 = 6.7 knots

You are already getting hull speed. Hope this clarifies things a little.
IN miles per hour the ratio is approximately 6/5 so 6.7knots = 8.04 MPH

1 nm =2024 yds or 6072 ft 1 stature mile = 5280 ft approx. 6/5 per NM

Regards Art

[hanleyclifford]

Hi Dan - Yeah, it's not an exact science for sure - kinda like bracketing an artillery target. The key thing in my experience is to move by stages from a known prop spec. A good shop can safely add 2" pitch to a prop that has not already been altered. Regards, Hanley

[Marian Claire]

Dave: Thanks for the #s. That gives me something to look for. It might be weeks before I can do another test. I guess I could do it at the dock as MPH is not needed.
Art: Sorry for the confusion. My "I get 6.7 knots" refers to my math not actual performance. Performance #s are in the first post.
HC: How is T-ville? Glad I am doing this now. With the forums help when I do haul the MC I will know how to proceed.
Still no takers for question 3? Dan S/V Marian Claire

[ndutton]

Dave's suggestion of a larger diameter prop whittled down with a more square profile at the ends is interesting. As long as you're planning on modifying a prop anyway either in pitch, profile or both, maybe take that same 15" prop and give it Indigo winglets. If it doesn't work you could still do the square modification.

[hanleyclifford]

Dan - Re question 3. I couldn't quantify this but by going to 13x11.5 from 13x13 my boat gets to 6 knots with ease whereas before I was lugging at 1800 and the A4 was not happy. Now I loaf along at 2000 but can easily get 2200 if I need to make a bridge. I firmly believe this is a trial and error exercise peculiar to each boat. Lot of empty slips here in Titusville - come on down! Regards, Hanley

[Marian Claire]

Yep. I just want someone to say " I pitched up 2"s and I now run .5 MPH faster than before at all RPM". But as stated It isn't that simple. T-ville sounds good. Its 12 and snowing with wind chills in the -#s.
Winglets? Hmmmmm Dan S/V Marian Claire

[CalebD]

Hmmm.
This discussion is making me wonder if I really am over propped with a 13" x 8" two blade prop on my Tartan 27'. The prop sits in a small aperture (like Marian Claire) and there is a hull diagram here: http://sailboatdata.com/viewrecord.asp?class_id=826
You Catalina 30' guys all seem to use a 12" x 7" or something but your prop shafts are out in the open, not in an aperture. My boat is about 2000#'s lighter then a Catalina 30.
Does a small aperture for the prop warrant the use of a slightly larger prop?
Hmmm.

[hanleyclifford]

13x8 sounds like a lot of prop for a direct drive. What is your cruise rpm?

[jpian0923]

Caleb,

I recently installed the Indigo 3 blade, 10", 7.4 pitch blade on my Islander 29.
http://sailboatdata.com/viewrecord.asp?class_id=691

It's much like your boat. I love it. RPM's are up by 500 (had hull cleaned too.) compared to the previous prop I had. (that one fell off the shaft as I was backing out of the slip one day. It's still in the mud somewhere.)

[CalebD]

13x8 sounds like a lot of prop for a direct drive. What is your cruise rpm?

Yes, direct drive.
I believe that we rarely get our tach over 2000 for cruising in flat water, which is low compared to what I read many of you report.

I'm getting a new shaft and I will have Shawn's 12" and my old 13" prop for our shop to evaluate. I am leaning heavily towards trying the 12" prop at this time.

I was just wondering if a prop in an aperture in front of the rudder required a bigger prop then a free standing prop like on a Catalina 30'?

[Marian Claire]

Caleb: I agree that you are probable over propped. From what I have read if the prop is sized correctly you should be able to turn 2400 or 2500 rpm, I have also read 1800 as a absolute minimum,with the direct drive. Like Dave's #s in post 12. It should be 3000+ for the 2 to 1 boats. There seems to be a bunch of over propped direct drive A-4s. If you have a wide, blunt end on the keel just forward of the prop it can affect the props performance. In my case the keel is about 4 or 5 inches wide and it is about 5 to 6 inches ahead of the prop. As best as I can tell this is just enough clearance. The wider diameter prop gets more blade out in "clean" water. You have to be careful with a aperture. There are minimum spaces that must be maintained in all directions. 15% of blade dia from the tips, 15% of diam from prop to rudder, 30% of diam from keel to prop are the #s I was given. FWIW. Dan S/V Marian Claire

[joe_db]

I think I get about 2700 RPM flat-out with my Indigo. When dealing with a prop-shop, make sure they know it isn't a diesel. A diesel will be damaged if not able to reach redline. This is not the case for the A-4. A direct drive prop reaching 3500 RPM wouldn't be a good choice for most displacement hulls.

[sastanley]

I want to put a 2:1 reduction drive on my C-30...I think that will tell the tale....except I'll have to cut up the galley, (and sell my Indigo prop). :rolleyes:

I wonder why more 2:1 reduction systems weren't designed with the A4, since about 99% of diesels have them, and their max RPM's available are much lower. :confused:

however, joe_db's comments are very valid with the differences between gas & diesel.

[Dave Neptune]

Caleb, you are pretty much spot on with your assumption regarding a larger prop in an aparature. On a prop running on a free shaft in the open all of the prop gets good water flow. However in an aparature a bit more diameter is usually required due to the blockage of water flow to the inside diameter of the prop and the loss when the blades are blocked by the deadwood. Going to a bit more diameter just brings you back to a comparable amount of water being swept by the blades, a very slight increase gives you a lot of "sq inches" swept because your gain is on the outside of the diameter. Sometimes as little as a 1/2" in diameter can make a huge differance because of the lare area that the outside diameter sweeps. Another thing to watch for is a 2 blade pulsing when running to few RPM's (lugging), as the prop hides behind the deadwood in it's rotation it looses and gains "bight" (traction) and that pulse can transfer through the entire boat. This is also an additional load on the thrust bearing. For the reasons stated above is why most "traditional" cruising boats with an aparature run a 3 blade, it won't pulse. The down side is you can't hide it inn the deadwood while sailing.

Dave Neptune :cool:

[lat 64]

I want to put a 2:1 reduction drive on my C-30...I think that will tell the tale....except I'll have to cut up the galley, (and sell my Indigo prop). :rolleyes:

I wonder why more 2:1 reduction systems weren't designed with the A4, since about 99% of diesels have them, and their max RPM's available are much lower. :confused:

however, joe_db's comments are very valid with the differences between gas & diesel.

I'm running a 16-inch prop on a 2:1.
I have been reading up in Dave Gerr's Propellor Handbook, and I am finding that the original spec for my boat is just about right. A recurring idea in his book is; bigger is better if you can swing it. Of course it's not that simple, but the idea is a larger, slower prop is more efficient. A reduction gear about doubles the torque at the shaft, making it possible to run a larger diameter prop. This lets the engine run with better(lower) cylinder pressures too.
You need a big place to swing a big prop, so I suppose the choice to use a direct drive was a clearance-issue compromise for the old production boats we have.
I'll post the specs on my boat after I find the info.

happy new year all,
r

[CalebD]

Thanks Dave Neptune, Russ and all for your input.
It seems that free standing propellers can be smaller as they get more bite in the water then a prop set behind deadwood in a fairly small aperture, like on my Tartan 27': http://sailboatdata.com/viewrecord.asp?class_id=826
I'm learning a lot more about props, shafts and drive train issues then I thought possible, thanks in no small part to this forum.
The guy at the prop shop who I took our drive train stuff to explained to me that the 'governor' of the engine (I'd always wondered about this) is the size of the prop hanging on the back of the shaft. He also suggested that with a new Cutless and new shaft we would be able to ramp up our cruising RPM's into the 2000+ range since we always tried to stay below that because of vibrations caused by a worn shaft that caused vibrations. This also helps explain why the 2:1 reduction drive is a good idea on heavier boats while 'swinging' a larger prop.
So now I have two props: the original 13" x 8" and Shawn's 12" x 6" from his Catalina 30' to choose from. Shawn's prop is in better shape then our old prop so I think I'm going to pay him for it and keep it even if I don't use it this season; I should try it out though. The reason for keeping the 12" x 6" prop is that our old prop is likely a bit, well, old and has lost some zinc (dezincification - thanks for that term Bill T.) and I'm not sure how many more seasons it can handle.
What spooks me a little is that some info I have on the Tartan 27' says that the original spec prop was 13" x 12" x 1" which I'm guessing most would say I was 'over propped' if I had such a prop.
It is a guessing game to some extent but trial and error will rule out.
Thanks again for everyone's input and advice.

[Marian Claire]

Caleb: 13x12x1 two blade is one of the props listed for the 2 to 1 gear. From this list,http://www.cncphotoalbum.com/atomic4/atomic4specs.htm, your 13x8 two blade is 3" of pitch to much for the direct drive.
Does the literature you have spec the gear ratio? Dan S/V Marian Claire

[Marian Claire]

[[[Edit: Disregard these #s. I found that my tach was way out.]]]
Will post corrections later.
Ran some vac #s.
I know my tach may be a little off and this was done at the dock. RPM then vac #
900 17
1400 17
1600 17
1800 16.8
2000 15+
2200 14
2400 12
2600 10
2800 8
3000 6.5
3200 4
Dan S/V Marian Claire

[Dave Neptune]

Dan, your numbers look good. They will increase a bit on the water and will increase more as the rpm's increase.
Did you try WOT?

Dave Neptune :cool:

[sastanley]

I cannot imagine how good an A4 sounds running at 3000+ RPM. It must be singing!!! :cool:

[Marian Claire]

Honey what did you do today? I used a phototach to check my tach this AM. Found my tach to be way off, reading 300 to 400 or more to high. No wonder I go so slow. Any way I redid the tests and will post #s later. But she hit 4 on the vac at 2700 RPM by photo and 3400 by MCs tach. I then pushed her up to WOT and the RPMs increased slightly and the vac dropped to 0. As I turned to write down the results POW SIZZZZ. The head cracked below the alternator bracket. I have a spare head and gaskets on board. I have the head off and will start putting her back togeather soon. Glad this happened here/now. Dan S/V Marian Claire

[Marian Claire]

Also I do not have a torque wrench with me . How stupid is it to snug up the nuts and test run then tighten them to spec when I get a wrench??? Just wondering. I was thinking what would I do if I was out in the boonies. Dan S/V Marian Claire

[lat 64]

Also I do not have a torque wrench with me . How stupid is it to snug up the nuts and test run then tighten them to spec when I get a wrench??? Just wondering. I was thinking what would I do if I was out in the boonies. Dan S/V Marian Claire

I can't see a problem for just storage but,...
I wouldn't run it of course.:eek:
Torque is just torque. I actually torqued one of the hard-to-get-to nuts on my A-4 with an open-end wrench and a scale. The one under the hose. If you were in the boonies, you can use a fisherman's weight scale and put it on the end of your wrench.
A little math is involved: at 1 foot from the center of the turning nut, 1 pound of force equals 1 foot-pound!

You need 35 ft. lbs right?
Say you have an 9-inch long wrench. That's only .75 feet. So you need to pull even more than 35 lbs. 35 is 75% of around 47 lbs.
Most fish scales are notoriously bad, so calibrate it with a known weight first.
A gallon of water in a milk jug would work. (1 Gallons [US] = 8.345 Pounds) plus a tiny bit for the jug.

[lat 64]

I need to add that my post is for a situation that requires action. like, some one on board is having a baby!
A torque wrench eliminates all the calculations and lets you concentrate on assembly. Go to K-mart and buy one. leave it on the boat for a fish club.

[Dave Neptune]

Hey Russ is that torque wrench good for "Socketeye Salmon":D?

Jus couldn't resist:o

Dave Neptune :cool:

[Dave Neptune]

Dan, that's horrible:eek:! Did the beastie get rough or noisy at WOT just before she cracked, or did you just spot it?

From what we've gleened regarding your tach you may be proped about right. FYI The reason most vac gages (not the test type) only go the 4" on there scales is that is a point where very little is gained thereafter on load duty type engines. And even in a hi-reving breather there is not much left at that point.

Really take your time torquing the new HEADGASKETS once you get to that point. Send me a PM for a few controversial tips if you like, or a # and we can chat. My head has been down for 28 years now:rolleyes:, with no leaks.

Dave Neptune :cool:

[hanleyclifford]

Dan - If that happened in gear on the dock it seems IMO that you are under-propped. I would not even want to be capable of 3000 rpm under those circumstances.

[edwardc]

... But she hit 4 on the vac at 2700 RPM by photo and 3400 by MCs tach. I then pushed her up to WOT and the RPMs increased slightly and the vac dropped to 0. As I turned to write down the results POW SIZZZZ. The head cracked below the alternator bracket. ...

Wow! Sorry to hear it! :( At least it wasn't in the middle of the sailing season!

I wonder what made it crack so abruptly? My first thought was differential heating, caused by a partially-obstructed cooling passage. Might be worth checking out the block's passages now that you have the head off. Are you raw water or fresh water cooled?

[Marian Claire]

Just got a torque wrench and did a round at 20 ft/lb and will work up to the 35 spec. Will try and answer ?s later. Dave I will PM with #. Thanks to all. Dan S/V Marian Claire

[Marian Claire]

Update and answers. Everything is back together and she runs fine and no leaks.. Torqued everything to 35 then did a warm up and retorqued.
Lat: I did get a torque wrench but I really appreciate the FT/LB/torque explanation. After your explaination I thought I could get a block and rig up one of my anchors to provide 33 lbs. Would probable get me home.
Dave: Thanks for the call. There was no noise just pop and water was spraying. The A-4 keep humming along or singing may be more acurate.
HC: I never hit a real 3000rpm due to the bad/off tach. I maxed out at 2700+. I did not have time to get a good rpm at WOT due to the head issue.
Ed: I did clean all the ports today. They were not to bad as I had cleaned them when I rebuilt in 2008. But she was RWC until about 2 months ago and had been used alot, two trips to Fla and the Abacos. I also flushed the system with fresh water at first start up this evening before I refilled with antifreeze.
Shawn: Sorry I do not know what a A-4 sounds like as the following #s will explain.
I will give three #s. MC tach - photo tach - vac #
1050 710 18
1400 980 18
1800 1210 18
2000 1450 17+
2400 1860 15
2800 2160 12
3000 2400 10-
3400 2700 4
WOT ? ? 0 pop spray etc.
I want to thank this forum, Don Moyer and MMI. What I have learned here alowed/gave me the confidence to do what I did today. If I missed a ? let me know. Dan S/V Marian Claire
Edit: So after all this I will hopefully go out and get some actual rpm/mph #s and see how my prop is. I did edit the earlier posts to show the bad #s.

[sastanley]

Dan...awesome report...you are out there "doing it" & living to tell about it.

They only time I can get my A4 over 2,200 RPM is in reverse with the howling reversing gear overshadowing everything, that's why I asked...I bet it sounds great the faster she runs (until she springs a leak of course..) :o

[lat 64]

Good work.
Torque wrenches really help you get a feel for things. Use it to put on your lug nuts on your car the proper way. It's surprising how easy it is to get 75 lbs! I found that I was over-torquing my wheel nuts back in high school, so I use a torque wrench every so often now to keep my hand used to the right amount of umph. I taught my daughter that way too, so she can safely put a wheel back on a car when she gets a flat.

[jhwelch]

Are the air guns at garages set to 75 ft-lbs? On a previous old car I used to remove and retighten the the lug nuts when it came back from the garage. It was quite a struggle to loosen them and not spin the wheel (there was hardly any weight on the back tires), so I thought it was better to do this under controlled circumstances than in an emergency. I had the wheels off often enough for other reasons (break work) that this made sense.

[sastanley]

jhwelch, Most garages claim to use something called "Torxstix" (sp?) that only allow 75-80-90 ft/lbs. or whatever your vehicles specs are. I systematically started elminating tire shops in my area when they kept warping the brake rotors on my car anytime I had tires balanced, etc.

I would ask them to not overtorque the things because I had been having trouble warping rotors (oh sir, we use blah blah..) but at the same time you can hear the impact guns hammering away in the background. I got to where I would go pick up my car and right in the parking lot pull out my wrench and torque the lugnuts in front of the shop before I left. Sometimes it was too late and the rotor was already warped, but sometimes I could save them if I hadn't driven the car yet.

Stupid shops. If only I could get the tools & equipment at home to set my own beads and a tire balancer, I wouldn't have to rely on those stupid tire people either. :mad:

[Dave Neptune]

Dan, take a good look at the tach and see if there is a switct on the back like ~4~6~8~ cylinder. I think you are in the 6 cylinder mode. On some old tachs it is use a differant wire and there are usually 3 of them (again 4~6~8).
I have found that checking tachs on hi-performance stuff is not as necessary as it was years ago as the tach's have gotten much better with electronic improvements. I would surely check to see if you can just "switch it". There were also tachs of old that were specific for a given # of cylinders.
If there is a way to switch it, don't worry about the inaccuracies from there, if your within 5~10% (you can check) your fine.
If not post a pic and what you can fronm the tach and maybe it can be figured out without bearing the expence of a new one.

Dave Neptune :cool:

[Marian Claire]

The tach is a Faria??. It does have a switch but it is on the 4 cyl setting. As we discussed I will be paying alot more attention to the Vac #s and less to the RPM. I am warming her up for another torqueing and if the SCA is lifted I may take her out this PM. This has been a long strange trip and I fell like a dumbass for not realizing that the tach was so far off. It sure explains many things. I had to reset my oil pressure and timming because everything had been set by the MCs tach. I guess one cold day I can go thru all my old posts and correct the #s.
Is it safe to run her up under load after the third torque or should I baby her for awhile? I have been running some under load but at low rpm to warm the engine. Dan S/V Marian Claire

[Dave Neptune]

Dan, take the t-wrench and shut her down while out if you can. I wouldn't run any harder than 8" until I got no movenment when retorqueing twice:rolleyes:.

Dan try switching the tach, it's old and things like the switch may not be lined up on the inside. Knock it back and forth a few times and it may work fine. Might try some "contact" spray around the switch when knocking it around:eek:.

Dave Neptune :cool:

[Marian Claire]

Will do. Thanks for the info. No movement on this last, third, round at 35 ft/lbs. Maybe I can hit the tach with my new torque wrench. NOT. Dan S/V Marian Claire

[edwardc]

This past summer, my tach started reading twice what the actual RPMs were. Even though the switch was in the "4 cyl" position, I rotated it back and forth several times through all the positions to clean the contacts. It came back to the correct readings and was fine the rest of the summer.

[Marian Claire]

Removed the tach and worked the switch back and forth. Also sprayed with contact cleaner as best as I could. Did not seem to improve/change and I will replace the tach "some day". The tach has read this way since I got the boat so what ever the problem is has been there for 8+ yrs. Ran the A-4 hard enough at the dock to get the vac # to 10. I hope to do some on the water tests in a few weeks.
Helped a friend move her 40 ft Caliber up from Morehead City today. Nice, nice, nice boat and it was good to be on the water again. Dan S/V Marian Claire

[jhwelch]

My previous tach was acting this way and I finally took it out and looked inside; the circuit board was full of corrosion so I had to replace the unit.

[Marian Claire]

Several questions. I have read a few posts on repairing cracks in the head and there seems to be several options, JB weld, epoxy and welding at a shop. Does this crack look to big to repair? What repair do you prefer? Would you keep a repaired head as a spare? Can the repair be tested? The head is 47 yrs old and has been in service for 40 yrs all RWC.
Also could I have opinions on the color variation on the valves shown? Mainly the white, #3 #4 versus the clean #2 exhaust valves. More pics here. http://www.moyermarine.com//forums/album.php?albumid=97
Dan S/V Marian Claire
PS. Anybody got a early model head sitting around collecting dust? And yes the access is that good on the MC. I only had to remove the alternator, crossover and temp sensor to remove the head.

[Laker]

I jumped in at the end of this thread , sorry if If this has already been brought up - the location of the crack makes me wonder if it is lifting ring related.

[Marian Claire]

Laker: Several of the posts I have read about cracks mention the lifting ring. As best I know I am the only one to ever remove the engine. I did not use the ring but used a sling made of webbing to remove and reinstall. I do not know how it was installed by the original builder back in the 60s. The mechanic at the marina looked at it and simply said " old Age". Who knows, uneven heat, as mentioned by Ed, some time in its life, years of vibration from the alternator??? As old as it is I may be wasting time trying to repair. Dan S/V Marian Claire

[hanleyclifford]

Dan - Any reason why you are limiting your search to an early head? You have plenty of room for the "thermostat bubble".

[Marian Claire]

HC: None other than my plug and play approach to spare parts. Would I have to modify my early manifold to accept a fitting for the hose/crossover or can the late head be changed/drilled to accept my early crossover tube? Dan S/V Marian Claire

[hanleyclifford]

Dan - The only thing you would need to do is tap the manifold for 1/2" NPT and then cobble a tube to the "bubble".

[ndutton]

Dan,

If it were me I don't think I'd attempt a repair of any kind, it would be a source of stress and worry. And I agree with Hanley, any head will do.

There has been much speculation over the lifting eye causing cracks. It may be a contributor in conjunction with other factors such as decades of salt water cooling and the ensuing corrosion substantially reducing the material thickness internally in that particular area but I suspect the lifting eye by itself isn't the cause. Dan's mechanic summarized this quite eloquently in two words, "old age."

Dan's experience is an example. He's never lifted his engine by the eye yet he has a crack. Can't blame his on a lifting operation. Also, every one of our engines was originally installed with the lifting eye. If the eye alone causes cracks, why don't we all have them or at least a significant percentage? No, there are other factors involved.

[Marian Claire]

HC: I have zero experience at tapping. So could I remove my existing early crossover tube, tap the manifold on the boat and replace the early tube and run with the head I have on? Then have a spare late head set up with one T-state housing port plugged and the other set up with a hose and fitting to tie into the tapped manifold. No T-stat would be used, same as my existing system. Again I just try to be prepared for a breakdown in the boonies. Dan S/V Marian Claire

[hanleyclifford]

Dan - Yeah, in fact I would get rid of that cast crossover tube even if using an early head - it is a nasty restriction. And I'm sure you could operate that tap.

[Dave Neptune]

Dan what is your hurry that one only lasted 40 years or better. Yeh I must agree with the old age senario. As far as the lifting of the lifting eye I doubt that would cause any damage unless really haddled roughly. I like the sling idea better.
Your valves and such look OK and remember that this shut down wasn't a normal one. I'd give the seats a good look and maybe kiss them and the valves to redo the seats.
Personally I would go for any "good" head I could find, the A-4 kind. Adapting one to the other is not rocket science. Welding via stitching is a good approach but for MY boat I would opt for the sure thing a good head! A welded head can last a long long time or a very short time no real way of knowing. My guess is since these heads are thin and flat I would stay away from any welding on the head where yours is cracked. If it were a small crack around a stud hole I MIGHT re-concider.

Dave Neptune :eek:

[Marian Claire]

Good deal. On the late head I see that the early exit port is blocked but still "located". Can that port be drilled and opened? Just looking at all my options.
Dave: Thanks for that on the valves. They just looked so different I had to ask. Dan S/V Marian Claire

[Marian Claire]

Anybody need a paper weight rated for high wind zones, hurricanes and Santa Anas. Dan S/V Marian Claire

[Laker]

Niel ,

I agree with your comments and opinions regarding the lifting ring , including the fact that it is , in all probability, not a factor in the MC case. That said , I still believe that it is a stress source which is best to avoid. But then , we've all hashed this out before.

Back aboard the MC ...

PS - Wife looked at photo of heads in cockpit and said : "muffin tins?"

[ndutton]

A couple of members have come up with improvements on the lifting eye design, Thatch being one of them. He added an ear that picks up a third head bolt that resolves the twisting leverage on the original design. I don't think he'll mind me posting this picture of his work.

[thatch]

I certainly don't mind Neil posting "almost" any of my photos. This bracket is similar to what "ILikeRust" had created, but is a bolt-on rather than a weld-on. Part of the reason for adding this part was to help insure good alignment of the alternator along with strengthening the lifting ring.... The only thing that I regret, is not having cleaned the grout better before taking that picture.
Tom

[Marian Claire]

Had a chance to get the MC out and run some tests. This time I had a properly functioning tach and in open water. It was not dead calm but what little breeze there was was always on the nose or beam. I averaged the speeds for each rpm.
RPM MPH Vac
1500 3.9 18+
1800 4.4 17+
2000 4.9 17
2300 5.7 15
2600 6.4 13

At this point the wind was up enough that I felt it would effect the test so I just had to sail the rest of the way home. Poor pitiful me.
When I first started this thread I simply wanted more speed. Now I want more top end speed, good "cruising" speed at a good continues use RPM and no lugging of the A-4. I will monitor the #s in the future but my conclusion at this point is that I am indeed slightly under-propped. Dan S/V Marian Claire

[Dave Neptune]

Dan, Hanley should be jealous of these numbers!! Yes they do indicate that you are indeed underpropped. At 2600 RPM I'd like to see between 5+~7" of vac. That would still give you a bit of reserve power, IE tha last few inches of vac without the worry of over-reving the beastie.
When re-propped you should achieve your 6.4 when clean around 2200 or less RPM with plenty of reserve power remaining to tow in a dead diesel while smiling profusely:rolleyes: and sipping the beverage of your choice from your MMI coffee mug;).

Dave Neptune :cool:

[hanleyclifford]

Hanley is paying strict attention to this discussion with a view to making a change. I want to cruise at 2000 rpm, however, and I am not real concerned about top speed. Staying tuned...

[Marian Claire]

Dave: The #s you suggest are very close to what I want to achieve. I will definitely post an update when I re-prop.
Hanley: I look forward to your results. Our boats and style of use are similar. Will be interesting to see where, prop wise, we end up.
Dan S/V Marian Claire

[jtsails]

Dan,
I'll throw some more numbers in for you. These are from memory, I left my notebook on the boat last weekend, but I think they are correct. My boat is a C&C 38 with an A4, 2:1 reduction, 16x10 two blade. No vac gauge.
WOT 2850 rpm, 6.7 knots
2600 rpm, 6.6knots
2400rpm, 6.4
2200 rpm, 6.2

My engine is a Stevedore model, and although I haven't looked yet, I am willing to bet that the restriction ring is still in the manifold. Your investigation is really tempting me to put a vac gauge on it just to satisfy my curiosity. Bringing the boat down from Maryland the last couple of weekends, we ran the motor a lot (close to 40 hrs) and ran it pretty hard at times. Never had a hiccup, she ran like a champ. It does burn about a quart of oil every 8 hours and we burned just over 1 gph on average for the whole trip.
James
S/V Delaney
C&C 38
Oriental, NC

[Marian Claire]

JT: Thanks for the #s. As I have learned during this process RPM, speed and vac #s all add to the picture of how well the prop is matched to the boat/A-4.
I hope to be out and about on the MC around Easter so if you are down in Oriental give me a shout. Dan S/V Marian Claire

[Dave Neptune]

I was working on my beastie last evening and thought about your cracked head. We have seen a few of these and I am wondering if the alt bracket is working as a heat sink and drawing (rediating) heat off the head causing a "chilled" spot which is already under stress. The sides of the bracket work as "veins" rediating heat from a concentrated area. I'm kinda reachin' here but thought I'd toss this out for your thoughts. I have seen "odder" things happen in some cases.

Dave Neptune :cool:

[edwardc]

... and I am wondering if the alt bracket is working as a heat sink and drawing (rediating) heat off the head causing a "chilled" spot which is already under stress. The sides of the bracket work as "veins" rediating heat from a concentrated area. ...

What an interesting idea.

Sounds like we need a fancy infra-red camera (preferably video ;) ) to take pictures of an A4 head under various conditions. Kind of like the ones they use to evaluate a house's winter insulation. (but I guess you southern California guys wouldn't know about stuff like that! :D )

[hanleyclifford]

I begin to see the logic in the idea, different coefficients of expansion for steel and cast iron...are we working at the frontier of Afourology?:)

[Ball Racing]

My head was cracked when I got it.
It was always RWC.
When I vee'd the crack with a dremel and cut off wheel, and spot drilled it to JB weld it,,,,,
It was not much more than over a 1/16" of a inch of metal left.

Possible this side of the head see the most erosion from water flow direction?
When I run mine even under hard load I can lay my hand on the head and leave it, so I don't think the bracket is making the condition much cooler.

I feel some people running without a thermostat and the constant cold water just rushing into the motor is as much a problem as anything.
One side of the head is a combustion chamber with thousand degrees in it, and thru a quarter inch of iron if your lucky you have water sometimes not even a 100 degrees.

That makes it hard for metal to stay stable...

[Marian Claire]

A few details. The crack I experienced was in the exterior layer of the head. The inner layer was not compromised. The fact that water immediately sprayed and there are no external clues, discoloration, peeled paint etc makes me think the head was getting a fairly uniform flow. On removal some of the ports were restricted but none totally blocked.
I have the head at a friends shop and hope to investigate the crack next week. Will check on the thickness of the metal.
I do not understand how not having a T-stat would cause this problem. I believe the original design for the A-4 did not use a T-stat. On my and all the A-4s I have seen the water/coolant enter the side of the block and works its way up, thru and out the head. On the RWC system and new FWC system I have used recently the water/coolant entering the block is warmer than the water the boat is sitting in due to the recirculating loop. I could see the block/head getting shocked if the engine was run for awhile and then the thru hull opened but that was not the case here. Dan S/V Marian Claire

[Dave Neptune]

Daniel, I could see the water flow being an issue as it should be a consistant flow. I have not used a t'stat for over 26 years now and the head has been down for that long as well. I also run in water that does not get below 50 degrees. I kinda doubt that the heat sink is a culprit but just a contributing factor. The bracket also distribute its "load and vibrations" directly through the bracket.
I am also wondering if the cracked heads are after market or stock Universal heads?

Dave Neptune :cool:

[Ball Racing]

In the car world, just because you ran with no thermostat , did not mean you were always running as cool as the gauge said you were,
as the water was running out so fast it never got a chance to "pull" the heat out of the metal parts.
I have the moyer bypass kit , the gate valve and checkvalve.
Lots of people say they control their temp with the valve.
I wonder if your really "always" changing the temp of all the metal areas, or just adding a extra flow of incoming water that cools the temp probe????

I think maybe we need various gauges at various places, and maybe even temp gauges that check block (metal) temps, not water temps.
We are worried about the temp of the oil, and moving parts, for over or underheating, not just the water..

Just as a thermos jug can be hot or cold on the inside, and you don't know it on the outside.:)

[Marian Claire]

I am 99% sure that the head that cracked was the original cast in 1965.
I received my used late model head, that I plan to use as a spare, the other day and noticed that 5 of the cooling ports are blocked. The three near the T-stat housing and two more down the water jacket side of the engine. My early model head had all the ports open. ???
I was concerned about the water vs metal temp issue so tried to monitor it. My water temp sensor is at the outlet of the manifold. I used my low tech oven thermometer to get a reading on the head itself. The base of the thermometer was wedged between the head and the manifold where the #2 and #3 exhaust ports are. It usually reads about 20 F higher than the water temp. When I turn off the engine the water temp rises to the block temp which makes perfect sense to me.
I will say that when I close my recirculating loop valve the water temp drops quickly. The block temp drops also but at a slower pace.
I have a small magnetic thermometer that is designed for use on a wood stove. I use it to monitor flue temps for safety as I heat with wood. I will try and take it with me on my next trip down to the MC and move it around the head and record temps. Never a dull moment. Dan S/V Marian Claire

[hanleyclifford]

A question seems to arise here: does a faster coolant flow rate result in more or less heat extraction/exchange at a given point? Let's hear from the engineers with knowledge of thermodynamics.

[Dave Neptune]

Dan, your absolutely correct about the speed at which the water moves through the system. On the A-4 with no T'stat you must use the bypass valve to restrict the volume going throught the engine to "maintain" an even temp. The only heating issues I have had in 26 years were when it was time to flush and once to replace the pump.
I had an interesting problem happen on one of my last cruises last season. As I was departing the marina I noticed the temp was a bit warmer than it had been so I popped the cover once in the outer harbor to take a look and give the bypass another nudge to closed and it did not respond as it usually would~~Hmmm~ somethings wrong. After pondering and looking around I decided that my water flow was far less than normal :eek: not good. So I pulled the intake off the strainer and the water just dribbled instead of gushing out :D found it, the problem that is. By now I am about 3~4 miles out of the harbor and only able to achieve 3.5 kts and I want to get to the island for an afternoon hike. I removed the hose at the thruhull and tried to poke through the valve and t-hull to no avail. It is mounted with a 90 where it comes through the hull due to space restrictions of the slole. Damn, need to go over the side with no one aboard and really did not want to do that. So I had a beer while "Ray" was still driving. As I sat and pondered I wished I had a diver or an air hose~ah hah~ an air hose would work but none on the boat. Then I spied a fire extinguisher and an idea formed!!! I stuck the hose back on the thru hull and stuck the extinguisher in the hose and duct taped it as well as I could. After hitting the handle and a big ga-dush. The hose and fittings were clear but not the cabin as the extinguisher did bolw off the tape and dusted the engine and myself and water was gushing out of the hose. And now there were some pretty confused crustations in the middle of the channel :D.
Dan On any H/P application I always modify the t'stat with a bleed hole as the engines are apart and back together often so one needs to insure that the system fills properly before making power. Don't neglect intake water temp changes if you run with no t'stat as it does make a difference. If your diverter is in proper orientation and operating order the heat distribution should be fine but it does take it a bit longer for the heat to settle as opposed to the t'stat. The main reason I run without is to keep the cabin cooler when motoring, the beastie is under my dinett and we often motor for 5 hours to get to the mooring before the wind starts and while the admirals ~ wife daughter and the Giz ~ are getting there beauty sleep.

Dave Neptune :cool:

[edwardc]

A question seems to arise here: does a faster coolant flow rate result in more or less heat extraction/exchange at a given point? Let's hear from the engineers with knowledge of thermodynamics.

A faster coolant flow definitely results in more heat extraction. It also results in lower coolant temps.

The rate of heat transfer between two substances is directly driven by the temperature differance between them. The faster flowing coolant doesn't get a chance to heat up as much, and keeps the temperature differance larger, driving a greater heat transfer rate.

[hanleyclifford]

A faster coolant flow definitely results in more heat extraction. It also results in lower coolant temps.

The rate of heat transfer between two substances is directly driven by the temperature differance between them. The faster flowing coolant doesn't get a chance to heat up as much, and keeps the temperature differance larger, driving a greater heat transfer rate. So does it therefore follow that a faster flow rate thru the A4 will result in more uniform temperature throughout the block ?

[ndutton]

The rate of heat transfer between two substances is directly driven by the temperature difference between them.

And how long they're in contact with each other.

Coolant flow rate through the block is the same rate as through the heat exchanger. Inside the HX a slower coolant flow allows more heat to be extracted from the coolant - within limitations of course.

The point of use commercial water heaters (Insta-hot) are shipped with faucet restrictors to slow the flow through the heater to allow the water more time to pick up heat. It makes a dramatic difference.

A similar example is the old skool restrictors that were used in place of thermostats on Chevy small block engines.

[edwardc]

And how long they're in contact with each other.

Coolant flow rate through the block is the same rate as through the heat exchanger. Inside the HX a slower coolant flow allows more heat to be extracted from the coolant - within limitations of course.

The point of use commercial water heaters (Insta-hot) are shipped with faucet restrictors to slow the flow through the heater to allow the water more time to pick up heat. It makes a dramatic difference.

A similar example is the old skool restrictors that were used in place of thermostats on Chevy small block engines.

Don't confuse heat-transfer-rate with total-heat-transferred or temperature. Three different things. Temperature is a function of heat-transfer-rate and time (and a few other things, such as the specific heat of a medium and its volume). Heat-transfer-rate (eg - BTU/hr) is a function of the temperature differential between two points and the thermal-conductivity between them. Total-heat (eg - BTU) is a function of heat-transfer-rate and time.

In the case of the water heater, you're shooting for maximum water temperature, not maximum heat transfer. So slowing down the flow rate allows the water to get to a higher temp, but it simultaneously reduces the heat-transfer-rate.

Consider this thought experiment. In your water heater, if the water flow is reduced, the water temp gets hotter. If you reduce the water flow rate all the way to zero, the temperature of the water eventually rises all the way to the temp of the water heater's heating element. But now the differential temperature between the heating element and the water is zero, and the heat transfer rate is also zero.

Conversely, if the water flow rate is increased, the water temperature gets lower, and the temperature differential between the element and the water gets larger, and the heat-transfer-rate goes up.

Interestingly, the equations that govern all this look just like the ones that govern electricity. For example, Ohms law is

Voltage = Current x Resistance

whereas for heat, we have

Temperature-difference = heat-transfer-rate x thermal-resistance

In our A4's cooling system, the heat-transfer-rate at any point in time depends on the temperature difference between the block/head and the coolant at that point in time (as well as the thermal-conductivity, ie - how clean your cooling jacket is). Running coolant faster lowers it's temperature and increases the heat transfer rate. This higher heat-transfer-rate starts to lower the block/head's temperature, and thus starts to lower the heat-transfer rate, until everything settles back into equilibrium at a new, lower, temperature, with the cooling system still removing all the heat the engine is producing, but now at a lower temperature.

[hanleyclifford]

Ed, That last post is really good and important. Could you transfer it over to Bill's new thread on controlling temperature?

[Marian Claire]

Follow up to post 79. After grinding out the crack in the head the metal was 1/4 " thick. We may do a repair and then pressure test it.
Also I had a plate made that fits over the opening for the T-stat housing on the late model head I got. The plate is 1/8 SS so I should still have enough threads on the studs to fully engage the nuts. I will plug the temp sensor hole and pop out the "freeze plug" under the crossover tube and turn a late model into a early model head.
Anybody know why some of the cooling ports are blocked off in the late heads? I can understand the ones right under the housing but why 5?
Compare parts pic and the one I posted in post # 65. http://www.moyermarine.com/cgi-bin/shopper.cgi?search=action&category=OVCM&keywords=all&template=Templates/B000_storebuilder.html
Dan S/V Marian Claire

[Marian Claire]

Had a chance to run the A-4 for another test session on open water and the results were similar to those in post #69. Have set up with a diver to pull the prop and get it to the prop shop. Now the 10,000$ question. How much would you change the pitch? 1" 1.5" 2". Dan S/V Marian Claire

[Dave Neptune]

Dan, as I recall your tach was off and your last was 2700 RPM @ 4" of vac correct? If so 2" is probably safe and should give you around 4" @ 3200 or a bit less, just a guess. An inch and a half would still be good and would probably yield 3500 at WOT. Based on your RPM's to speed what speed do you want to cruise at? I recomend a setting of around 7" for "fast cruise" which gives you a bit of power to overcome windier conditions when present and the engine can spin and loaf along easily the rest of the time.

How many RPM's per inch of prop on the reduction units? And how fast are you going at 7" of vac now?

Dan, note your are going in the unenviable direction regarding pitch. When pitching "back" props tend to wash out as the "rake" is more negative and results are often disappointing. Pitching up is the better way to go as it increases "rake" and "bight" at the same time. Might want to check around for a used prop that is closer or one you can trade for and pitch "up".

Dave Neptune :cool:

[Marian Claire]

I need to make it clear that I am pitching up.
Dave: You are right. On one test, at the dock, and I emphasize at the dock, I read 2700 RPM on a photo tach and read 4 #s on the vac back in post #42 just before the head cracked.
I have since installed a new tach and have done the tests in open water. I think the open water tests are more representative and useful. Post #69. Frankly I have been reluctant/gun-shy to push her much past 2600/2700 RPM and in real world use I do not want to run 2600 all day.
I am assuming that the 2 to 1 would not change the pitch change to RPM change relationship.
I want to cruise at 6.5 MPH at about 2300 RPM and a vac of say 9.
I am guessing/estimating that if I pitch up 2" I will hit 6.4 MPH at 2200 RPM and the vac should drop 4 or 5 #s to say 8 or 9.
Does that sound reasonable? Dan S/V Marian Claire

[Dave Neptune]

Dan, took a look and wow. 13" at 2600 is really loafing along for 6.4mph. What is the pitch of your prop now? If you were getting 6.4mph @ 13" of vac the engine is not making very much HP which truly indicates you don't need much for 6.4. Also how fast in mph can your "hull" do?
If you go up 2 inches you will lower the vac numbers at all rpm's and increase speed up to your max hull speed. 2 inches is a lot depending on where it is at now IE adding 2 inches to 8 is 25% & 2 inches to 12 is 16%. These relation ships change considerably depending on where you start from.
If your vac rpm speed numbers in post #69 are good 2 inches should make a considerable improvement. The conventional way to calibrate is at WOT rpm vs where you need or want it to be at WOT and then let the rest of the range be. Any marine engine diesel, gas or OB to perform to "specs" needs to get to max rpm at WOT to perform properly and avoid ligging.

Dave Neptune :cool:

[Marian Claire]

Dave: Thanks for the continued responses. I know this thread has been hard to follow with all the inaccurate #s I used early in the thread.
Theoretical hull speed for the MC is 7.6 MPH. I have never been able to determine the pitch of the prop and will only know it when it is removed and goes to the shop.
Knowing that all open water tests are not exact I still think I can extrapolate some #s and hope they prove close. I "think" it would take about 600 more RPM to go from 6.4 MPH to hull speed. With my present prop that would be hitting 3200 rpm and I do not want to run that many RPM even for short runs. If I pitch up 2" and all my guesses are close I should hit hull speed around 2800 RPM. Also have a good cruising speed at 2300 RPM which falls right in the mid range suggested RPM for A-4s in continues use and that is very important to me.
I will wait until I know the existing pitch before I decide exactly how much to add and realize that no one can tell me exactly what to do. I am mostly seeking advice to avoid doing something stupid. Thanks again. Dan S/V Marian Claire

[Dave Neptune]

Dan, do you have a guess from speaking to someone in a similar boat? How about the diameter? Also as I recall MC has a bit of deadwood and an aparature correct?
Sounds like 2" should be enough.
And BTW the vac gage measures in inches of mercury not pounds. The higher the number is more vac and "O" is atmospheric or WOT sort of.
Your water line is probably close to mine, Volador has a great deal of overhang at the stern.

Dave Neptune :cool:

[Marian Claire]

Unfortunately similar boats are hard to find with the MC being home made and all. Hanley's is close. I am maxed out on diameter, 14", unless I start cutting wood. The deadwood just forward of the prop is so thick that I do not want to reduce diameter and lose the props ability to run in "clean" water.
The prop is scheduled to be pulled tomorrow and unless I hear something weird from the prop shop I will go with a 2" pitch up and see what happens. Thanks for the reminder on the terms. It is important and makes a big difference in understanding posts. LWL 25'. Flying Fish?? Dan S/V Marian Claire

[Ball Racing]

Alot of talk of vacuum,
do we have any data showing the a-4 wearing any part out fast because of vacuum being low, meaning you are apply alot of throttle?
I think I would rather tune by exhaust gase temp, then vacuum reading as that would give you a better reading of the effect of cylinder pressure, if in fact the a-4 wears badly at full pressure..

With the torque curve of this motor, the low rpms it was designed around, the low cylider pressure, I think this motor can stand WOT for ever,
compared to how easy it is to cook a car engine in a boat, of even a diesel, both of which are reaching alot of pressures, that they weren't made to perform in.

[Dave Neptune]

Dan, indeed the A-4 is a robust design for the HP it puts out. I have worked on 50HP rotaries you could hold in your hand. The exhaust temp (or O2 sensor) will tell you if the engine is burning efficiently at any RPM or load. The vac gage only measures what the manifold is delivering and with the same boat & prop if you maintain RPM and increase the vac you have made a gain in power efficiency for the individual application. If you see a decrease in RPM's and the load (vac) is the same something is amiss and because you have tuned well the temp/O2 sensor will still read fine. It measures the efficiency of the burn not the load.

Dave Neptune :cool:

[Marian Claire]

The first thing I thought when I held the MCs prop in my hand was, " What narrow blades". After cleaning her she is marked 14 X 10 RH. IMO A 14 X 10 should be a good match for the MC so what is the problem. The maker is Austral uphttp://www.australpropeller.com.au/fixedyacht.htm and that explains alot. My blade width is 25% of diameter. I think 33% would be more normal. Off to the prop shop in the AM to see what my options are. Dan S/V Marian Claire

[ndutton]

My blade width is 25% of diameter. I think 33% would be more normal.
Michigan Propeller's Sailor 2 is 36%.

You know those Aussies, probably works better spinning backwards.

Correction:
The 36% is E.A.R. or Expanded Area Ratio. It's the ratio between the area of the blades to the area of the circle described by the diameter of the propeller. There's another ratio that compares the projection of the blades to the circle, takes blade pitch or blade twist into account. I can't remember right now what the other is called, the B.A.R. or the D.A.R., something like that. The E.A.R. is usually higher than the other.

[Marian Claire]

Some good, some ???. I had the new prop installed today. It is a 14 X 9 three blade. It was bored for 1.25" and my prop shaft is 1" so we used a sleeve to make up the differance. The vac #s look good from my dock testing. I seem to have lost about 2 "s from the old prop. That is right at what I was looking for. Will try to do open water tests in the AM but more SCA here so who knows how good they will be.
I do have a whine/chirp that was not there with the old prop. It kicks in around 1300 RPM and maxs at 1500 RPM and drops off from there. At 2000/2200 RPM I can still hear it but it is faint. It is not in the A-4, reversing gear or 2 to 1 reduction gear. There is no movement in the drive shaft to prop shaft coupling. No vibration that was not there before. Just noise.
Any advice?
Will post pics of the old and new prop when I get home, land home that is.
Dan S/V Marian Claire

[sastanley]

Dan, My chirp was the shaft on the shaft log...Harmonics mean something is out of whack. Mine chirped for 33 years at certain RPMs before it was a big enough problem that I had to rectify it.

YMMV. :cool:

[edwardc]

...
I do have a wine/chirp that was not there with the old prop. It kicks in around 1300 RPM and maxs at 1500 RPM and drops off from there. At 2000/2200 RPM I can still hear it but it is faint. It is not in the A-4, reversing gear or 2 to 1 reduction gear. There is no movement in the drive shaft to prop shaft coupling. No vibration that was not there before. Just noise.
Any advice?...

We had a lot of discussion on this thread (http://www.moyermarine.com/forums/showthread.php?t=5254) last year about "prop singing" at certain rpms.

Coincidentally, I just had my boat "short hauled" yesterday to clean the bottom and scrape & repaint the prop. I took that opportunity to put a small bevel on the trailing edges to try and cure it, but haven't taken it out yet. As soon as I do, I'll bump the thread with the results.

[Marian Claire]

Thanks guys. Very good thread Ed. The pic of RobH2's prop is just like mine. What do you call the part that is attached to the hull? SCA thru tonight but should be calm enough Friday to do some test runs. Will keep an eye and ear on the whine. Dan S/V Marian Claire

[edwardc]

Don't know what it's called, but it sure looks like it's a holder for the cutless bearing. That looks like a set screw on the side.

I've read that many here have the bearing directly installed in the "deadwood" directly ahead of the prop, with the setscrew set in the fiberglass. This looks like a much more robust solution, less likely to let the bearing slip.

[Dave Neptune]

Dan et all, there is a good pic of a prop on another thread that you can "see" the grind used to rduce prop singing. Look at the outside edges of the prop all the way around the blade there is a "counter swirl" of grind marks you can see. Those are ground and a very very very slight angle on the drive face and a bit more of an angle on the back side. The slight strain put on the blade from the "angle" is not perfect and eliminates the harmonic vibration that is the singing. The chirp can also be cavitation as the blades pass through the deadwood restriction.
The pic is post #60 in CalebD,'s thread Shaft removal~~~~~~11/29/11 in the Driveline threads. When I first saw the pic I thought of I think it was Edwards singing prop last year, not sure it was Edward though.

Dave Neptune :cool:

[sastanley]

Now you don't have to go look for it.

--> link to that post #60 (http://www.moyermarine.com/forums/showpost.php?p=52079&postcount=60) <--

And here is the pic re-posted here..:D

Caleb, I am still amazed with the work. That looks nothing like the piece of garbage prop I sent you..:rolleyes: :o

http://www.moyermarine.com/forums/attachment.php?attachmentid=5642&stc=1&d=1334115789

[Marian Claire]

The mechanic stopped by the marina and I snagged him for a listen. Same results. No vibration, max whine at 1500 rpm. He suggested I loosen the stuffing box to a heavy flow and test. That produced no change so a lack of water in the cutless does not seem to be an issue. After he left I ran it in reverse at 1500 rpm and no whine!!! The new prop did not have any of the grinding or edge angle as best as I could tell. The leading edge was also much sharper than my old prop. Consensus seems to be run it and see what happens. Dan S/V Marian Claire
PS. If Hanley and PT are out in the Albermarle and it is blowing like it is here they are in for a exciting ride.

[Dave Neptune]

Dan, the whine should change as the prop dirties up and becomes less symetric, at which point it should begin to quiet. Not uncommon especially on a fresh prop. Any compitent prop guy should be able to "fix" easily but you will have to get it to him or get busy with a file yourself. If you do don't take much especially on the thrust side facing aft.
I recomend you use it as is until you either want to rid it of the whine and/or you are sure you don't want to give it another tweak.
The whine will not hurt anything unless you are of the Ulysses type:eek:, then tie yourself to the stick within reach of liquid bread, a video in hand and send us vids of the lovelies.:D

Dave Neptune :cool:

[Marian Claire]

Results from first open water test are very positive. I will spare you all the #s but here are a few.
2300 RPM 6.3 MPH 12" vac
2600 RPM 6.8 MPH 9" vac
2800 RPM 7.1 MPH 8" vac
There is less variation in the tail wind, head wind, beam wind #s. The MC actually "squats" and puts out that rolling wake like other boats. This is all new. The whine is much less in open water.
Look forward to seeing how she does in current and head winds.
Thanks to all. This has been a long process but worth the effort.
Dan S/V Marian Claire

[Dave Neptune]

Dan, those numbers look good for using all available :rolleyes: from the A-4. Did you try a WOT at all, I'm guessing 3200 is about where it will max out. This is a rarity form what I have seen on this forum for the most part. At your 2800 with 8" your cylinder load is pretty low, just more burns in the same time frame so you have reduced a great deal of preassure on the rod bearings and the crank bearings will be happier too! You even have room to possibly add a bit more pitch.
The whine is less noticeable underway because the harmonics with water flowing past the hull will change the pitch and range of the "song" your prop is singing. Like is said don't worry to much about it as it has a good chance of going away once a lil growth starts. Your so close to "perfect" now any changes should be slight and patiently thought over from experiencing this prop for a while. If the "song" drives you nuts oor it is easy to get the prop removed go-4-it.

Fair winds my friend _/) _/)
Dave Neptune (\_ :cool:

[Marian Claire]

Had a chance to take the MC out in less than ideal conditions for motoring. 15 to 20 and gusting higher, 2' to 3' breaking waves of very short period. With the old prop in these conditions I could not maintain speed and would always fall off when I hit a bigger set of waves. Ended up spending a lot of time regaining speed and getting back on course. With the new prop I lose a little speed when I hit a bigger set of waves but was able to push thru and not fall off. Much easier on the helmsman.Stopping power is unreal and reverse actually works and is controllable. I do agree I could bump up a little more in pitch but will run this for awhile.
While the prop was of I pulled the rudder, removed the temporary repairs and do a more permanent repair. The rudder is two large pieces of mahogany and one of the original rods had corroded allowing the upper area to separate. Pics of the props and what got sucked in the RW intake during a dock test. That is some kind of grass. Dan S/V Marian Claire

[Dave Neptune]

Dan, good to hear the power is getting to the water! That's how it should work. When you were running hard aginst the wind and sea what were you reading RPM vs vac? Did the vac values go up a bit out on the water compared to being tied to the dock?
Excellent choice to run the prop for a while before making any further adjustments! You may still have some available power left and be able to cruise a bit faster at lower RPM's yet~but wait my friend and see how it works when a bit dirty!!! Then decide;).

Dave Neptune :cool:

[Marian Claire]

[QUOTE= When you were running hard aginst the wind and sea what were you reading RPM vs vac? Did the vac values go up a bit out on the water compared to being tied to the dock?


? 1. I did not get any vac #s during the "rough" conditions test. Just to awkward to do single-handed with the vac gauge in its present location. IIRC Somewhere around 2000 rpm gave me good steady forward progress without excessive pounding. My GPS speed was all over the place so any guess at speed is just that, a guess. Say 4 mph???
? 2. Yes. Checking my notes the vac # was 2"s+- higher on the open water test than the dock test at the same rpm.
Dan S/V Marian Claire