Yanmar 3GM30F engine, burning oil--Why? Can you help?

[ewsponberg]

Hi Everyone,
You have helped me generously before, and I'd like some help solving the following problem. Our boat, Corroboree, is 30 years old with its original Yanmar 3GM30F engine (SN: 560). When we bought the boat two years ago, the engine surveyor estimated that there was about 3,000 hours on it. We have added 160 hours to that since launching.

The problem is, this engine burns a lot of oil, about one quart every 16-20 hours. It should not burn oil at all. There are no oil leaks in the engine, the bilge is perfectly dry. The engine is a little hard to start when cold, and there is some blueish white smoke on starting, but that quickly dissipates. Once warm, the engine starts fine. The engine runs fine, too--smooth, with no excess noise or vibration. To handle this situation, we carry a lot of spare oil on board, and we monitor oil consumption religiously. A number of Yanmar mechanics have said we are facing an engine overhaul in the near future, so we are saving our dollars for that.

But my first question, for you mechanics, is what is causing the oil consumption? The various mechanics suggest either valve seals are leaking and have to be replaced. OR, the piston rings are worn and have to be replaced. Any thoughts? Are there any simple tests that I or a mechanic can do to would precisely pin down the cause so that we can determine a method of repair? I'd like to know more about the possible symptoms before going through exploratory surgery to tear the engine down in order to find out what's wrong.

The second question is about where to do this work. We are currently in the Dominican Republic at Ocean World Marina near Puerto Plata. Local sailors suggest cobbling together a repair plan and doing the engine repairs here. Getting parts into here is hard because of customs and importation red tape. Others suggest having the work done in Puerto Rico, including the Yanmar dealer in San Juan, but if you know anything about sailing against the Northeast Trade Winds, from here that is nearly impossible. We can get to the south side of Puerto Rico without much trouble, but getting direct to San Juan is not really in the cards. So, question: Can you suggest any mechanic or engine repair firm in Puerto Rico, or the DR, that you would trust to do a good job on scoping out the problem and getting our engine fixed?

Thanks for all your help in the past, it is most appreciated.

Cheers,

Eric