1996 115 Crossflow Milky Plug

Hey everyone!

I have a 1997 Northstar LTD jet boat with the famous OMC 115 Turbo jet, Ive owned the boat for about 6 years now. About 3 years ago I rebuilt the motor (myself) because it ate a ring in cyl #1 and #3. Its been running good knock on wood since, but fear I may have a problem again.

After a week or 2 with no use I decided to check the compression to see health. 3 were at 130psi even, and 1 was at 110psi. The one that was lower had a little touch of milky oil on the plug,

Anyone have any ideas?? I mean the motor still performed great after taking it out but I dont want to cause damage that I can prevent, maybe the head gasket?

Also to note,,,,,, last year I randomly got the overheat alarm go off out no where for a bit then shut off. Its never happened before and heck I didn't even think it worked. But it never came back on for rest of the summer.

Appreciate the read and any ideas or opinions.

If you are running the oil injection system, you might want to check the oil reservoir for water.

If that is not the source of the water, perhaps a gasket in the exhaust system is leaking a bit.

BTW- water in injection oil tank is very bad for motor lubrication.

Yes sorry I should've mentioned the oil injection system had been deleted! I run the traditional 50:1 oil mix in the gas.

OK, that cuts it down to internal engine issues.

One of the experts on your engine will be along to advise on what portions of the engine to check. The last Johnnyrude V4 I had was from 1959.

Were the heads resurfaced ( flat ) when it was rebuilt?------Properly winterized if in a freezing climate?

Yes heads were resurfaced. And always winterized properly and kept in my garage here in Ontario!