Questions about A-4

[ISerenity]

I just purchased a 1978 Islander 28. It is in pretty good shape and there seems to have been some serious work done on the engine. My family and I planned on motoring the boat from Fort Myers Fl through the Okeechobee to Stuart Fl.

As we got underway our oil pressure was at 50 over the coarse of 1.5 hours we continuously lost oil pressure until I shut the engine down when it got to 10. I was concerned that we lost oil somewhere; however, we had lost none. The dipstick read full.

The next day we headed back to Cape Coral and the same thing happened.

The engine also has a loud knock in it at low RPM.

One more thing: how fast should I be going at 2000 rpm going with the wind and current. I was only going about 2-3 knots and other sailboats were passing me like I was standing still.

Thanks,

Andrew

[Dave Neptune]

Andrew, first welcome to the forum. Your speed at 2000 RPM is a bit slow but since the engine is spinning that fast it is probably a dirty bottom and prop. It suprises most people how much a dirty bottom can slow the boat down~~probably not an issue.You say you have a loud "knocking" sound at idle and that may be and probably is the culprit. It is probably a rod bearig giving up or possibly a main bearing (doubtful). The bearing is knocking because it is either badly damaged or worn and it is hammering back and forth against the crank producing your noise. The extra gap allows more oil to pass through it becauuse of the additional clearance. As the engine runs the oil slowly warms and thins out so it is easier for more oil to squeeze out of the offending bearing. The oil pump is a positive displacement type so as the volume of oil being pumped more and more of it is being allowed through the gap as it heats up. The oil pump volume becomes to little for the preassure valve to maintain that preassure so it gradually drops as the oil warms.
You could try checking the adjusting valve but I doubt you will find anything amiss there.
Sounds to me like you will unfortunately need to pull the engine down to repair the knocking bearing.
One more thing is the knocking there when you start cold or only after the oil preassure begins to drop? Fresh oil of thicker viscosity may mask the problem but not fix it.
Sorry for the "not good" reply. And again welcome to the forum. Anything you need to do can be assisted by the members of this forum.
Good luck!

Dave Neptune :cool:

[Loki9]

Try pulling the spark plug wires off one at a time while the engine is running. If the knock goes away, you have found the cylinder with the bad rod bearing.

Check out this thread: http://www.moyermarine.com/forums/showthread.php?t=5352

There is a video demonstrating what a bad rod bearing sounds like.

[lat 64]

Andrew, first welcome to the forum. Your speed at 2000 RPM is a bit slow but since the engine is spinning that fast it is probably a dirty bottom and prop. It suprises most people how much a dirty bottom can slow the boat down~~probably not an issue.You say you have a loud "knocking" sound at idle and that may be and probably is the culprit. It is probably a rod bearig giving up or possibly a main bearing (doubtful). The bearing is knocking because it is either badly damaged or worn and it is hammering back and forth against the crank producing your noise. The extra gap allows more oil to pass through it becauuse of the additional clearance. As the engine runs the oil slowly warms and thins out so it is easier for more oil to squeeze out of the offending bearing. The oil pump is a positive displacement type so as the volume of oil being pumped more and more of it is being allowed through the gap as it heats up. The oil pump volume becomes to little for the preassure valve to maintain that preassure so it gradually drops as the oil warms.
You could try checking the adjusting valve but I doubt you will find anything amiss there.
Sounds to me like you will unfortunately need to pull the engine down to repair the knocking bearing.
One more thing is the knocking there when you start cold or only after the oil preassure begins to drop? Fresh oil of thicker viscosity may mask the problem but not fix it.
Sorry for the "not good" reply. And again welcome to the forum. Anything you need to do can be assisted by the members of this forum.
Good luck!

Dave Neptune :cool:

I'm afraid I'm with dave here on this one.
I had much the same symptoms, but my engine was just poorly rebuilt. The mechanic put the wrong size bearing shells in, resulting in a large oil clearance in the main bearings. The oil pressure was high until it warmed up and then fell off to nil. The previous owner or his mechanic had turned the oil pressure adjuster all the way in to compensate but it was a poor band-aid fix.

Baby that engine until you can get a good mechanic's qualified opinion to confirm our diagnosis.

save the engine for just docking for now.
Russ

[smosher]

fwiw on the oil pressure decreasing, I had a bad engine ground and one of the indicators was the oil pressure gauge would decrease as it ran.

Steve

[ISerenity]

I very much appreciate your input. The bottom and the prop were recently cleaned so I am wondering if I may need a more efficient prop. I have a mechanic coming this Saturday to take a look at it.

I read about the issue with the oil pressure going down with the electric gauge. I think the person I bought it from may have been dealing with this issue because there is an oil pressure gauge connected directly to the oil sending unit via a tube.

Two more things:

I am an avid believer in AMSOIL in diesel engines as I have had many through the years on my farm. I am considering using synthetic in this A-4. Are there any reasons not to?

Should I spend the money for a fresh water cooling system. The engine gets hot and does not seem to be cooling that well either.

[ILikeRust]

I am an avid believer in AMSOIL in diesel engines as I have had many through the years on my farm. I am considering using synthetic in this A-4. Are there any reasons not to?

Yes - the reversing gear shares the same oil supply with the crank case. The reversing gear consists of a clutch pack and a brake band around it. If you put oil in that contains certain friction modifiers, you can cause the clutch to slip. Synthetics are good for modern, high-tolerance, high-RPM engines, particularly if you want to go a long time between oil changes. I see no reason whatsoever to waste the money on expensive synthetic oil in our decidedly old-tech, low-tech engines. Just use good-quality oil of the proper weight and change it at least every 50 hours.

I truly think it would be a waste of money to put synthetic oil in an Atomic 4.

Should I spend the money for a fresh water cooling system. The engine gets hot and does not seem to be cooling that well either.

If the engine isn't cooling well, a FWC system might not fix that. Likely needs a good flush to clean out accumulated crud in the cooling passages. Also check the water pump to make sure the impeller is not worn and that it is pumping at full capacity. And check hoses and fittings for obstructions.

As to whether it's worth converting to FWC, IMHO, that depends on the condition of the engine and boat that it's in and your future plans for it. I converted mine to FWC because I perceived it to be worth the investment.

[edwardc]

... Also check the water pump to make sure the impeller is not worn and that it is pumping at full capacity. ...

Don't forget to check the backplate for wear too. Except for the o-ring slot it should be completely flat. It takes a surprisingly small amount of wear here to significantly affect the pump's output.

[JOHN COOKSON]

I read about the issue with the oil pressure going down with the electric gauge. I think the person I bought it from may have been dealing with this issue because there is an oil pressure gauge connected directly to the oil sending unit via a tube.

I28
You have a direct read oil pressure gauge.

If you haven't done so already:
Disconnect the tube at the gauge and flush some oil through it with the engine running. There may be an air bubble in the tube that is giving you a false reading.

Sorry but this won't help the knock.

TRUE GRIT

[Antibes]

I love my Islander 28. With anything close to a clean bottom the speed on your islander should be close to 5 knots at 2000 RPM. The a4 is a lot of power for this boat.

I would follow through with the advise given already. Add the FWC after you get the other issues first. Clean up one problem at a time so you know what the real issue is.

[Ajax]

This frequent mention of the oil pressure falling off after the engine warms up-

Is it always indicative of an impending major failure?

[Marian Claire]

Ajax: I can only speak for what happens on the MC. At cold start I have 55 to 60 psi. This slowly drops to around 18 to 20 psi at 800 rpm and 38 to 40 psi at 2000 rpm when the engine is warm. I have had times, it happens for no apparent reason, when the pressure dropped from 55 cold to 25 warm and at 2000 rpm and as low as 12 to 15 at 800rpm. This condition was corrected by cleaning and readjusting the oil pressure adjustment. I have the early cone type.
So I believe some drop is normal. The drop and knock described in the OP is not IMO normal. Dan S/V Marian Claire
Edit: 2000 rpm is my cruising rpm. I have the 2 to 1 reduction gear.

[JOHN COOKSON]

This frequent mention of the oil pressure falling off after the engine warms up-
Is it always indicative of an impending major failure?

The rule of thumb for A4 oil pressure:
~40PSI with the engine warmed up at cruise RPM and ~1/2 that at warmed up idle.
The oil pressure will of course be higher when the engine is cold.

TRUE GRIT

[Dave Neptune]

Ajax, it is normal for the O/P to drop a bit when the engine warms up. However if the preassure reading is lower when the engine is warmed than normal it could be time to change to oil as it is beginning to break down. This should only be aronud a 5 psi drop though. If it really drops and won't come beck up with fresh oil it can indicate that there is excessive wear on the bearings and the additional clearance (wear) allows more oil to squeeze by reducing the O/P.
The above assumes normal oil level.

Dave Neptune :cool:

[Ajax]

Thanks guys.

I do not have any knocking sounds, but I do have what sounds like either an exhaust leak tick or perhaps a stuck valve lifter.

I know that I'm due for an oil change, and hope to do it this weekend. I have also never adjusted the oil pressure doo-dad. (newish owner)

I also wonder about the integrity of my oil pressure gauge. When the engine is cold, the oil pressure reads 100lbs upon startup! It then drifts down gradually to about 20-25 psi after about 2 hours under 3/4 throttle.

I have lots to inspect and improve this winter. :) Sorry for the hijack.

[ISerenity]

I have printed out this thread to talk about your responses with the mechanic in the morning. When I get a diagnosis from him I will let you all know what he said. i very much appreciate all of you taking your time to help me.

Here is a link to my boat: http://www.youtube.com/watch?v=aR6y8xSlFt4

[lat 64]

Thanks guys.

I do not have any knocking sounds, but I do have what sounds like either an exhaust leak tick or perhaps a stuck valve lifter.

I know that I'm due for an oil change, and hope to do it this weekend. I have also never adjusted the oil pressure doo-dad. (newish owner)

I also wonder about the integrity of my oil pressure gauge. When the engine is cold, the oil pressure reads 100lbs upon startup! It then drifts down gradually to about 20-25 psi after about 2 hours under 3/4 throttle.

I have lots to inspect and improve this winter. :) Sorry for the hijack.
No sorry necessary. It's a forum:D
Could the oil be too high viscosity? 100 psi is sure a lot. I have around 50 at startup and I thought that was a bit too high. Definatly check into it. Maybe an oil change first, then get some baseline measurements.

Russ

[Marian Claire]

Iserenity: When you do go east do you plan to use the rim route or cross the lake? Several years back my wife flew in to Ft Myers and joined me for the crossing to the east coast. Wonderful trip. Dan S/V Marian Claire