Oil usage ?

[killin time]

I have a pair of Mercruiser 8.2 L gas inboards in my 36' Stamas express. They have about 950 hours on them and they both start and run exceptionally well. Other then being a little thirsty, (.65 gpm), the only problem I have is with the starboard engine. It starts immediately, runs great and does not smoke, other than condensation and about the same as the port-side. However, it uses about a quart of oil per hour of running time, and I can't seem to get the oil pressure above 25 lbs, as opposed to the port-side that runs a constant 40 lbs.

I've checked the whole engine for leaks and there are none. Is there a possibility that there is an internal leak in the oil cooler?

My next step is to do a compression check to see if there are any stuck rings, etc. I'm probably putting this off because I'm hoping for something simpler, and cheaper to fix.

Anybody have any luck with oil or fuel additives, such as Sea Foam or Ring Free? Would I be doing more harm them good by trying them?

My tanks are about 1/3 full right now so now would be the time to try a fuel additive.

[Capt John1]

You've got two problems, low pressure and oil consumption. If you've got a leaking oil cooler you should see a slick in the water coming out of the exhaust, you can get them pressure tested. Before you condem the engine I would hook up a temporary mechanical oil pressure gauge, you could very well have a bad gauge or sender unit. I would also pull the plugs, that oil's eather leaking out or being burned, if your burning that much oil you should have at least one very fouled plug. A bad oil ring may not show up in a compression check, a bad compression ring will. Is the oil leaking into the bilge? Try changing the oil filter, it could be clogged (but not likely your problem, are you using the right filter?). If you find nothing it's either the oil pump or the by pass valve. A heavier weight oil might also get you more time out of the engine. If you can get the engine out of the boat the pump and valve are easy to replace as long as you have fixed the oil consumption problem.

[killin time]

Absolutely no oil in the bilge, and yes I'm using the correct filter. Pulling the engine from the boat is not an option at this time.

I'll check the plugs for soot when I do the compression check, just looking for any other ideas before then.

I don't think it's a gauge issue because I'm losing the oil somewhere. I haven't noticed a slick, but that's a thought. I think I'll stick a 5 gallon bucket down there and collect some exhaust at start-up and see what I've got. Thanks

I'm using straight 40 weight oil now.

[prockvoan]

No leaks from engine leads me to think that you are burnning the oil.Chances are a valve seal can lead to burning oil or blow by of the rings.Remove all plugs,that will be your first telltail.If and when you do see which plug looks like cr-p,then you will know which way to go.Head job or rering it.