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oil in propeller exhaust

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Boatdrinks

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I have a problem of oil being ejected in the cooling system thru the propeller. It is quite significant. Are there ANY points in the cooling system where the motor oil can enter the cooling system?? This is an inline 6 250 older 165 Mercrusier a motor rebuild 260 hrs. ago. Any suggestions welcomed!!
 
Definitely motor oil, lower end oil full, no power steering. This is a 77 Rienell with straight 6 . had water in the oil, changed the manifold and riser and fixed that but now the oil is bleeding into the cooling system and being exhausted out the prop loosing a little less than 1 quart an hour. Makes a mess in the lake. Tried oil leak in a can no change. Sounds like internal block or water jacket breach but want to exhaust all possibilities before giving in to that. What am I missing??
 
If I had water in my engine oil, the first thing I would have done would be to run a compression test before I started replacing parts.
 
This has been an ongoing situation, the motor was my first thought. I pulled the head and replaced the gasket, because I was advised I had a cracked block or blown head gasket or warped or cracked head. As a part of that process we found a crack in the exhaust manifold so I replaced it with a used part I found locally (big mistake) and it seemed all was well for a short time. I then did engine tests including compression. All cylinders were good and even. Unless I am missing something I must have a hairline crack somewhere in the engine block. So now when it is running, motor oil is leaking into the cooling system and exhausted thru the prop and when it is shut down a very slight amount of water leeches into the oil. Appreciate all comments. Thanks so much!!
 
re: "and it seemed all was well for a short time"...

Back a lifetime ago, I had a car that specified @ the 1000 mile check, that the head should be retorqued. The dealer didn't do this. Car started to blow exhaust gas into the water jacket ( and out the overflow) when under heavy load even though compression test was apparently ok. A teardown of the engine showed a faint leakage track in the head gasket between the combustion chamber and the water jacket. you could just as well have a leakage track between the oil feed (40+ psi) to the head and the water jacket ( 5 ish psi). This would not show in a compression test.
 
Had that happened to one of my Chrysler inboards. The leakage damaged the block so much it needed a rebuild, so don't mess around with this if it's the problem.

Jeff
 
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