J/30 Class Association Forums J/30 Forum The Boat, Sails and Equipment Smoking Diesel

So my engine over the last season and a half has started to put out quite a bit of soot. I would say smoke but it does not really smoke more than it has in the past. The difference is that just at fast idle I do not really see any smoke but the transom gets covered with soot. And this can happen with just a hour of fast idle to charge the batteries.

I have changed the oil, cleaned the oil filter, changed the air filter and treated the fuel.

Any other suggestions?

You may have a clogged injector so that the fuel isn't atomized completely. Try pulling the injectors and cleaning the tips. You can probably just clean them up carefully with a wire brush and solvent. In the worst case, you may actually see a charcol briquette stuck by the pin hole where the fuel gets atomized. There is a picture on page 42 in the Yanmar Operators manual on what the spray should look like. A diesel repair shop can "pop test" the injectors.

If it's accumulations of soot, then I would also suspect the mixing elbow - that can accumulate carbon and restrict the elbow. You can remove the piece, soak it in oxalic acid, clean and stick it right back on (they can be a bear to remove).

Just running the motor at a fast idle to charge batteries is really, really tough on a diesel. They need to be under load. Using the motor to charge to batteries or chronically under-revving it (lots of people cruise at 1500 or 1600 RPM thinking they're going easy on the motor) can cause a condition called "wet stacking" that will accumulate unburnt fuel components on the exhaust side of the motor and on the cylinder walls. It will eventually damage a motor and shorten its life.

If that is really your only way to charge the batteries, try putting the boat in gear when possible.

Jason - It is not often that I charge the batteries that way and I like to drive the engine about 2400 rpm. I think I will take my mixing elbow off and give it a clean - as well as give the injectors a quick clean.

Thanks for the help.

David