OMC 3.0 Water in oil

[gwershing]

I have a 1989 OMC 3.0 (GM), sterndrive. I just rebuilt the engine. I have been having a tough time gettting the valves adjusted, but made progress by adjusting them with the engine running. I've taken it out twice, the first time I didn't have the shift cable adjusted correctly so I had shift problems; also, the valves were noisey. The second time I took it out I ran it for a while, then the engine quit from what I think was the valves seating and I lost compression. I assume that when I adjusted the valves, I made them too tight...but that's for another thread. The real question: After each time I took it out I noticed the oil had water in it after (light brown milk; Yes, I changed the oil in between trips). Being a car guy, I assume a head gasket, but I've been reading threads that talk about a manifold or elbow leak. I don't understand how water can get into the crankcase by a leak in the manifold. Perhaps someone can clear that up for me. Also, before I bought it the boat was in salt water, so there was some corrosion damage to the manifold and elbow. I did replace the elbow but not the manifold. Please help.

 

[sea wolf]

Re: OMC 3.0 Water in oil

It's an '89 & lived in salt water. You need a new manifold. Especially since you've found corrosion. You're lucky to get 5 years out of manifolds/risers that have lived in salt water.

 

[gwershing]

Re: OMC 3.0 Water in oil

Thanks for the info. Since most of my experience is with cars, I just can't picture how a bad manifold would allow water to get into the crackcase?

 

[cooter2506]

Re: OMC 3.0 Water in oil

Probably a hole in water jacket of manifold leaking into exhaust side of manifold then into cylinders and eventually into oil pan

 

[Maclin]

Re: OMC 3.0 Water in oil

The sea water pump draws in fresh water and pushes it to the engine's circulating water pump as if it was coming from a radiator. This is what the engine's water pump circulates for cooling. The thermostat controls how much water is brought into the engine, the excess is bypassed. The exhaust manifolds have two passages, exhaust and water. The spent and excess cooling water travels thru the exhaust manifold cooling water passage up to the riser then mixes with the exhaust and blows on out. This keeps the exhaust manifold temperature down inside the boat as well keeping the rubber exhaust hoses from melting. If the riser or manifold is corroded enough the chambers mix too soon and when the engine shuts off water travels down the exhaust passage and on into any cylinder with an open exhaust valve. This can hydrolock the engine the next time it tries to start. The water will also eventually leak past the rings into the crankcase oil. If it is salt water the engine will rust very quickly.

 

[gwershing]

Re: OMC 3.0 Water in oil

Okay, I understand. Now it seems obvious. The whole purpose for the elbow is to keep the water out of the exaust manifold.
Thank you.