Yanmar 6lp ste

[neptune]

My Yanmar is in big trouble. Looking for others who might have an idea of cause.

It is a 2000 engine with 1,300 hours after a complete rebuild several years ago. Has run like a top and has had good maintenance.

While at speed the engine started knocking. Turned it off. Oil was WAY low. I check it often and only 20 hours on fresh oil and filter. Added a gallon of oil. Ran like a top again. But after about an hour getting back to the slip it started to knock again. Oil was again way low. No smoke, no oil slick, no oil in the coolant. But there is oil in the bilge. Why is the oil leaving the engine? Mechaninc thinks it is a fuel issue. Too much, too little, or contaminated. Fuel is being tested now for problems. Mechanic is checking with a scope but he is sure rings are shot and maybe cylinders are scored. Not good!

What could cause the oil to leave the engine and wind up in the bilge?

Compression tests showed not good stuff. 5 cylinders were about 250psi with one down under 200.

So two things. One, Engine needs to be repaired/rebuilt. Second, what caused the problem to begin with.

Any ideas.

[Capt Brad]

Maybe an oil pan leak?

[catalina_mike]

An oil sample will show the dilution rate (fuel) and moisture. I would run a sample.... not only will it show those two items but rings, bearings have different metals and they will also show up in the sample and give clues.

[Paddy]

Based on the quick oil loss, I would say its the dreaded steel oil plug that I had in 2016. The years of saltwater splash from failing raw water pumps sits in the steel plug until it develops a hole. I poured quarts out in minutes. Check here…

[REBMystic]

Let us know how it goes & thanks for sharing to help us all learn. I have 6LP-STE engines of similar age, so I will follow this intently. I agree with the comments, and expect it is something where the plug / dipstick connects near the bottom of the pan. I just pulled all my HX and there is the oil cooler connections which could leak. But I expect unlikely as I don't think they'd leak at the rate you mentioned.
- Does the oil leak out when not running?
- Did you get low pressure alarm before the knocking?

Hopefully the situation is not as bad as you fear. Best of luck!

Rob