Yanmar rebuild

[Paul Stanly]

I have a 81 H-30 with a Yanmar 2gm raw water engine. Lately, it has been burning motor oil yet there is very little if any smoke and there is no sign of a leak of any king. The engine has 1920 hours on it 100 of which I put on her myself. I had a mechanic look at here and he stated that fuel is getting into the oil, and that a engine rebuild is warranted and the worst case would be around 3500 dollars. Does this sound right for this engine and the amount of hours and has anyone out there has similar problems?

 

[Claude L.-Auger]

Get a second opinion

Paul, at 1900 hours if that is really the case, that engine is still in its infancy unless it overheated very very badly (and it is almost impossible to ruin a Yanmar by overheating it !)First, If fuel is indeed getting into the oil, it would mean that the piston rings / cylinder wall clearance would have been enlarged or distorted enough to let fuel by. Which would also mean loss of compression. So, Get somebody to take a compression test before you let anybody that your money for a rebuild.Second, if diesel fuel is getting into the crankcase, that nasty black thick oil would not be as thick. You could have it analysed.You say it has been burning oil yet there is no smoke. How much oil do you have to add in how many hours of running the engine. I just took a 3-week trip and my 3 GMF took less than ½ a quart in over 75 hours of running time mostly at 2700 RPM. It does smoke a little, but other than having to clean the transom, it runs just fine.Since you say you only put in 100 of those hours yourself, call the previous owner and ask him what the oil consumption was when he had it.Good Luck

 

[George L]

Oil in crankcase

As previously stated, the diesel fuel dillution of oil is capable of washing out the rings and bearings. I strongly advise that you change the oil immediately with a diesel oil NEVER GAS AUTO OIL. I use Chevron delo, or Shell Rotella. If you feel the oil between your fingers after an oil change you will notice much greater lubricity. I suspect that you may have a bad injector or two, but I agree you need a second opinion. The injectors really need the water separator such as the Dahl or Racor in addition to the primary fuel filters. To help reduce the thinning of the oil, do not idle for long periods of time, this is hard on a diesel as you get poor combustion at low speeds. Depending on the temp. it is best to run a diesel at 900 rpm or more until it runs smoothly an makes a minimal amount of smoke.

 

[Steve Dion]

If it true?

Paul:If it's true that you only have 2000 hrs on a 2GM, it is like a baby in Yanmar years. The normal life should be between 10,000 - 12,000 for this type of problem.I think that George is on to something. One of the problems with using an Sx (engine for a spark engine - gasoline) rated oil is that it can cause rings to stick. This is one of the MAJOR differences between Sx and Cx (compression - diesel) type oils. I would contact someone that is familar with Yanmars and ask them if there is anything that can be used to clean up this problem without doing a rebuild.If they do not know of anything, I'd change the oil and use a high detergent additive. Run it hard for about 8-10 hours and change the oil again. Maybe do this a couple of times and then just use a Delo, or Rotella oil as a normal oil change.Never, but never use an Sx rated oil in a diesel engine. The only exception would be if you are low on oil and it is the oil thing available.This could also be a time that you may want TRY a synthetic for one of these changes. Be aware that synthetic can cause an older engine to leak. In your case it may be worth the risk.