Mercruiser 5.7 Smoke, Oil Consumption, High Oil Pressure

[sjenkinsk]

Installed a remanufactured Mercruiser 5.7 in my 1982 SR 225 Express Cruiser back in June.

The motor has puffed blue smoke, used varying amounts of oil and had high oil pressure since day one. Engine dealer says there is nothing wrong with the motor and that I have a lean problem.

No lean problem has been uncoverd but could still be possibiliy. Several mechanics have looked at the motor and said they believe it to be the valve stem seals.

My questions are:

1)Could the high oil pressure be causing my problems?

2)What would cause the high oil pressure.

3)Would the high oil pressure force oil through the valve stem seals and /or over the rings? The pressure is 80 at 4000 RPM, 40 at idle. I have checked the pressure guage and it is working correctly.

Changed oil and went for a spin yesterday and the oil pressure dropped from 80 to 60 at 4000 rpm after about 20 minutes or running if that means anything.

3)There has been oil in the bilge but I cannot determine from where it is coming. Could this be the relief valve letting off pressure?

4) Really not interested in spending a lot of money to remove and replace the engine again, so do I just live with this problem or is there a fix I am missing?

My thought is that the high oil pressure is causing my problems and that if I can bring the pressure down my burnoff would decline. But I know just enough to get in trouble.

Thanks for any assistance in identifying the problem and a remedy.

Steve J.
1982 Sea Ray 225 Express Cruiser
Mercruiser 5.7
Apha Drive, 16x16

 

[mvoellinger]

Have you changed the oil? I think that would be the first step, to make sure the proper oil is in there and that there is no oil contamination.

 

[BonBini]

Your oil presure is controled solely by the oil pumps presure relief valve. To test the relief presure, the engine needs to be run up with a manual gauge attatched, the presure will flutter when the valve starts to dump oil. Some times the test will need to be done with cold oil to get results at a lower rpm. To do any work to the reliev valve the oil pump needs to be accessed. You know what that means.

On the other hand: 80 psi is up there but it may still be within spec. As long as the relief valve is moving freelly I wouldnt worry much about it.

The oil consumption does suck. Make sure your not over full on oil. Pull the plugs and see if they all show oil or just one or two. Look at the breather hoses for oil flooding out. Clean the bilge and try to determin a general area of leakage, front back ... One quart oil leakage makes a huge mess in a bilge. Also one quart oil burned gets the transom pretty oily. ...Ron

 

[SR Tech]

When you say "remanufactured" are you talking about a crate motor? a short block? long block?

Did you make the necessary changes in your driving habits as far as a break in period?

^important questions in diagnosis

 

[sjenkinsk]

Long block from Radido Marine.

Yes, I followed break in procedure.

 

[sprink56]

Long block from Radido Marine.

Yes, I followed break in procedure.

I think you mean Rapido in Miami?...anyway...sounds like the oil is climbing up to the valve covers and may be leaking out. Make sure that you have good crank case ventilation. At 80 PSI gaskets are put to the test and standard cork gaskets will not hold at that pressure. You should have a filtered crankcase vent on each valve cover. That will allow the pressure to escape and not build up. Are you running the original valve covers or some aftermarket covers? Many of the cheap aftermarket covers don't have adequate baffeling to keep the oil from exiting the fill cap or vent ports. You know it is easy to have valve cover or intake manifold leaks and not see them. If you have used any cork gaskets on your valve covers or intake, replace them with high quality Fel-Pro, Victor or some other brand that has a metal insert (valve cover) to maintain the shape of the gasket. The intake at the rear of the intake is notorious for leaking on Small Block Chevys with big oil pressure. If it is leaking you need to plan on replacing it which means you might as well replace the whole intake set while you are doing it. Also make sure that you are not over filling the engine...make sure you know how many quarts are in the engine and don't trust the dipstick. Most small block Chevys for marine use carry 5 or 6 quarts + 1 quart for the filter. If you are not using the big filter and are using the "shorty" you are probably a half quart over full. I don't reccomend the "shorty' it doesn't have enough filtration area for marine applications.

These engines don't need that much oil pressure. These engine builders put high performance pumps on their engines so they will live. They have to warrant them so they do all they can to insure that they last. I have built many of these engines and can tell you that unless you are running in excess of 6000 RPM consistantly, a standard pump will serve you well and make it easier to keep the oil in the engine. This is just FYI and I am not suggesting that you change the oil pump...just relieve the crankcase pressure and use the best gaskets you can buy.:thumbsup:

You can work through this...it just takes a little patience and good equipment. Oil leaks are dangerous and a royal pain in the ass.:smt101

Good luck with it.