Think this needs antisiphon loop?

[rigspelt]

Think I need to install an antisiphon loop on the raw water line where it enters the exhaust stack 12" above the static waterline? I can't see how a siphon would get going into the waterlift muffler from the raw water throughull.

[keelcooler]

Yes it can happen and yes you need to install one. When I saw your set up I was not sure you had a siphon brake.Install on the red hose top of the loop affix a hanger so it does not sag down.The problem with vented loops,they leak.With time the spring and ball fail to mate well and drip leak when running.That's why many members find hoses fitted to the vent leading to the bilge or sink drain.

[sastanley]

Yes it can happen and yes you need to install one. When I saw your set up I was not sure you had a siphon brake.Install on the red hose top of the loop affix a hanger so it does not sag down.The problem with vented loops,they leak.With time the spring and ball fail to mate well and drip leak when running.That's why many members find hoses fitted to the vent leading to the bilge or sink drain.

Oh!..is that why I found one of those? I replaced my loop this winter, mostly because the bronze valve snapped off, so hopefully I'll be OK for a bit.

Rigs, I would add one. You aren't always sailing straight up & down. Also, add one on the head intake as well, unless you have easy access to the seacock and can turn it off every time you use it. Even sitting static, it can siphon in.

[keelcooler]

A siphon is a siphon no matter if the boat is upright or knocked down.Introduce air at loop high point,on more siphon.Not recommended for head intake line unless bowl is at or below waterline.Remember that if you don't properly secure above the waterline the air will not be allowed in the line to do it's braking job.In fact you could sink the boat when the little spring and plastic ball fail to seat.

[rigspelt]

I was afraid the votes would lean toward installing a vented loop. I am familiar with that setup in toilet plumbing systems. I guess if I've been thinking about it so much for this raw water coolant line, then safety says do it. The downsides are cost, time for installation, more holes in the cockpit wall to attach the fittings, regular valve checking, and sourcing a replacement valve down the road. The upside is less worry about flooding the engine.

Don's PDF on this issue is here: Please see attached.

I am not going to run a tube up the mast tall enough to counter the pressure in the line to prevent coolant from divertiing out the loop but allow air in when the engine is shut down like the old timers did, so I need a valve. The next question is whether to rig something myself from local parts, or order up Don's custom part KTAS_01.2_318 anti-siphon kit. As usual, we know the careful thought Don put into this kind of thing, and 5/8" hose barb fittings are hard to find, so off I go to MMI's online store.

[roadnsky]

rigs-
As you said, Don puts a lot of thought (and experience) into their products.
You know that valve is gonna work as well as having all the necessary parts. One-stop-shopping!
Depending on access :eek: it's a 5 minute project...

I've had the Anti-Siphon kit installed since November and it works great.
-Jerry

[Dave Neptune]

Rigs & the rest of you guys, the vented loop would deffinately be needed in your application. My application is very similar however my engine sits a little deeper in the middle of the boat and I have nowhere to mount the V-loop without making a run that contains almost enough water to backfill the exhaust when the vent breaks the siphon. HOWEVER because my v-loop has very little rise to it, so it doesn't take much corrosion to keep it from breaking the siphon :eek: filling the engine with salt water. After using many different V-loops and having to get the water out of the engine more times that I wish to admit to the first few years I had her.
What I have done is to modify a V-loop by removing the anti-siphon valve and installig a "Ball valve" thus making the system a manual operation. When I am ready to start the engine I close "the valve" and when I shut her down I open "the valve". the only time this fails is when "I do" which is far less than the "surprises" I found when the vent fails to open. I have been using this for about 20 of the 26 years I have been running my A-4. Admittedly this may not be the best alternative however it works everytime I remember to operate it.:o

Dave Neptune
1970 E-35MkII original A-4 still ticking!!!:cool:

[keelcooler]

You know the down side of not installing,so I know you will proceed accordingly.Take a look at Don's setup.All the cost is in all that brass.This is above water stuff so you can use PVC or other plastic.You can purchase that
PVC vent separately and cobble up the rest with hardware store plastics.You could do the valve deal above or go all plastic with a smallest you can find hose barb fitting at the loop top.Run a small hose down into the bilge.Yes it's going to leak (hopefully only drip) when you run the motor.We are talking about the next size up from pin hole.

[sastanley]

rigs, I installed a 5/8" marelon loop from Forespar, The cheapest place I found it was Defender. I originally had a heavy bronze one that came on the boat (factory) and the vent broke off when I was trying to muscle the hose on there. It was 3/4", so I couldn't get my 5/8" hose over the barbs anyway. I am glad it broke, it gave me an excuse to replace it with a proper sized one.

Since I have a Catalina 30, my loop is installed as high as I can get it in the galley cabinet directly adjacent to the engine. It comes up about 12" above the waterline if I had to guess.

Mine also was not mounted very well and worked just fine. I seem to recall a short sheet metal screw into the (wood) cabinet and some stiff wire holding the loop up..

Based on all of your postings here I can guess that you probably wouldn't let that slide and will properly install it..I use finish washers on the outside where screws have to go thru things and they help clean up the look nicely. I still hate drilling holes in the boat though, even if it is 30+ years old :(

[rigspelt]

rigs, I installed a 5/8" marelon loop from Forespar ... I use finish washers on the outside where screws have to go thru things and they help clean up the look nicely. I still hate drilling holes in the boat though, even if it is 30+ years old :(

I just got a Forespar marelon vented loop for the toilet (the old bronze one would not accept that nice Trident 1.5" hose) -- the Forespar product is very nice and inexpensive, and I know I can get replacement duckbills. The low corrosion factor is something to consider too. Their 5/8" loop would have been a good idea, but the MMI product has crossed the border and is making its way to our mailbox, so shiny brass it will be.

I like installing stuff like this with through-and-through skookum stainless bolts with low profile pan heads and a washer, or a countersink head bolt with countersink washer. In this case I'll also use a small plywood backing block on the inside. Nice thing about having painted this sturdy old fibreglass boat is that I can repaint to hide little messes.

[rigspelt]

Done. Seems to work fine based on a trial startup in the ocean today (splashed yesterday). I'll install a backing plate to stabilize the vent tomorrow. Great to finally see seawater pouring out the stern and hear that A4 music today, after all these months of refit.

[67c&ccorv]

She's looking good Rigsy - noticed you are using the "Mikalor" brand hose clamps.

Where did you find the all S/S version?:confused: (ie. the tightning screw appears to be S/S.)

[rigspelt]

Got those clamps at a local marine supplier, either Mermaid or Stright MacKay.

[sastanley]

Woo hoo! Looks nice. I can see the bright shiny motor hiding out down there purring away! :cool:

[rigspelt]

After running the engine a bit this am to try out the new carb, I pulled the 2" hose from the exhaust port on our new MMI stainless waterlift muffler. There was only 1" in the bottom of the muffler. Perfect. Phew -- the redesign worked out. The antisiphon valve is working perfectly too: gurgles nicely when the water drains back down to the throughull. Haven't checked the backpressure yet, but if engine performanc is OK I probably won't. Many thanks to everyone for their advice, and Don Moyer for the quality parts.