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2Scorpios 20-06-2009 09:09

Sea Water in Oil
I have a Yanmar 4JHE that I just overhauled completely (because of water in the oil) and re-installed. The original problem was thought to be a stuck exhaust valve that allowed water to be sucked in from the exhaust elbow. That eventually caused a bent connecting rod and broken cylinder liner.
Now the engine is back in the boat after successful bench testing and all seemed well... until I went out for a great sail and on the way back in I noticed black smoke and lack of power. Got back to the slip and checked everything and found I had the dreaded "milky" oil again! Apparently I'd fixed the baby chicken and not the egg! I've found that the egg was a plugged anti-siphon loop...
I've fixed that and drained the oil a couple of times, but it's still a little milky and though the engine starts and runs well at no-load, it bogs down under load at about 2000 rpm with black smoke.
Where do I go from here? I really, really don't want to take it out again!
Thanks for any suggestions....

camaraderie 20-06-2009 09:39

Do you have an oil cooler on the engine or tranny? Pinhole leaks in the exchangers can siphon water into the oil. Worth checking.

May I also put in a plug for Marvel Mystery oil once you have found the problem. You will need to do several oil changes in fairly rapid succession to get the remaining water out of the oil systems. A quart of MMO mixed in with your regular oil during those changes can really help prevent further damage. No affiliation with them...just had the oil cooler problem and followed that regime as recommended by a good diesel guy and it worked great.

David M 20-06-2009 09:49

Do you think water is still getting in to the oil or is there just some remaining emulsified oil left? It was not clear to me by your description. It would be two different solutions depending on which is the case.

Water getting in to the engine oil can come from quite a few different sources. Its best not to guess.

I don't know what your budget is but if oil is still leaking in I would get someone else to do the repair or the overhaul. This way if it is not done correctly then you have some recourse. For some things, it is sometimes better to hire a professional who has repaired these kinds of things before.

James S 20-06-2009 09:54 start with welcome to the forum.
What kind of boat do you have?
How long have you had this boat?
Was it the anti-siphon loop that was plugged or the valve...I'm thinking the valve.
Can you describe the exhaust system?

2Scorpios 20-06-2009 10:05

Thanks for the welcome and replies... The loop is fine, the breather was plugged hence the siphoning. The oil cooler is good. When I had the engine out and stripped, I pressure checked everything. I'm fairly sure it was the breather that was causing the problem all along and I've fixed that. I'm now just trying to get the emulsified oil/water cleaned out. I've done 2 changes and it's still a bit milky. I'll do a couple more and see what I get. I guess my real question is what effect all this has on the injectors or whatever, causing the lack of power - and what I should do about that part of the problem...

David M 20-06-2009 10:22

The lack of power initially sounds like a fuel supply problem. Although black smoke indicates too high a mixture or undercompression or an overloaded engine. I would have a professional take a look.

Getting the emulsified oil out is just a matter of doing oil changes until that goes away.

The engine oil will not affect the injectors in any way. Crud or water in the fuel that gets past the primary and secondary filters will affect the injector pump.

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