Yanmar 3gm 30f advice needed.

[justjohn]

So the old girl did awesome last trip to Granada got back to St Thomas and had her sitting in a dirty hole for about 3 weeks while I did life on the hard ( hate that). She was started a few times with no issues but never put under load. I get back on board and took off again. She started up but shortly after putting her under load at 2000 rpm she started with black smoke and carbon in the wet exhaust. Then couldn't take a load at all! Checked fuel and filter it was fine. Checked air filter and it was fine. Any ideas on what to check next? All advice would be welcome.


The Lady Euphoria

[djmarchand]

The Yanmar gm series engines are notorious for plugging the exhaust elbow causing exactly the symptoms you described. Remove it and if it looks fouled up with soot and scale, replace it as it is difficult to clean adequately.

David

[Cheechako]

Originally Posted by djmarchand

The Yanmar gm series engines are notorious for plugging the exhaust elbow causing exactly the symptoms you described. Remove it and if it looks fouled up with soot and scale, replace it as it is difficult to clean adequately.

David

I would start there for sure.

[justjohn]

Oh wise Yoda's thank you for the advice. I ended up taking the exhaust off the block and after a hit or two for myself soaked it in acid. Put it back on and she's purring like a kitten at 2500 rpm. I owe rum! And the little green men and pink elephants didn't hurt a thing! Thanks again my sailor friends!


The Lady Euphoria

[djmarchand]

And a hole could break through at any minute. Keep an eye on it. I would replace it.

David

[justjohn]

I hope not. It should get me where I need to go to get It replaced. I didn't soak it long. But thanks for the awesome thought. Thank God the boat has sails!


The Lady Euphoria

[wsmurdoch]

Several people have sawed plugged exhaust elbows in half to expose the mess inside. Search Google Images for "yanmar exhaust elbow" to see some of them and get an idea of what you will need to clean out to make it servicable. It took me more than four hours with a screwdriver and hammer in George Town, Exuma this year to clean mine out enough to get the engine (mine is a 3HM35F) to go over 2000 rpm. I now have a new elbow installed and carry as a spares a new second elbow and all the other parts from the manifold to the exhaust rubber hose.