Loss of power with black smoke.

[Ben Mesker]

So we are motoring along just fine (as fine as you can go with a 25 knot headwind.) The diesel was working just fine for hours (2200rpms cruising speed) then a lose of power began, rpms droped with the throttle still in the same position. The rpms went down to 1500. When more throttle was added the engine did speed up but then alot of black smoke would be produced. Ease off the throttle and the black smoke would go away. It was not overheating, there was nothing wrapped around the prop, oil and water seemed fine. It occured to me it could be a clogged air filter. When I removed the air intake silencer I found that there was no air filter. Isn't this where the air filter should be? I just bought the boat and I have no experience with marine diesels. Please help, By the way I have a 2GMF engine.

 

[Pete]

air filter

your engine has no air filer per say it should have a round foam cover that acts as a filter. check for a fuel leak as for your loss of power/black smoke

 

[Steve Dion]

Needs an air filter but....

Ben:You should have an air cleaner/filter. The canister is on the port side of the engine and there is a snorkle that should point down. The filter inside the canister is a metal cone with foam rubber over the cone. Not very expensive. Black smoke is usually an indication of too much fuel. I am guessing that you are having a problem with an injector. Be sure to check how much a new injector is before you have them rebuilt. Some are cheaper to replace than to rebuild. Depending how comfortable you feel about doing the diagnosis it may be better to have a YANMAR mechanic check this out. Be sure that you get a Yanmar guy out there. I hear too many horror stories about non-Yanmar mechanics working on these engines.

 

[Patrick Ewing]

Check exhaust riser for blockage

It is at the end of your exhaust manifold where the water is injected. Mine was blocked and caused these symptoms.

 

[Gordon Torresen]

Power loss and black smoke.

Your description sounds like you may have "lost" one of your cylinders. If the problem has not self-corrected, get the engine running and operate the compression releases, one at a time. If you have the link between the levers, get rid of it. If one release kills the engine, the other won't. The one that lets the engine keep running is the culprit. It could be that an injector is stuck, a valve is hanging, a push rod is displaced, the injector pump for that cylinder is stuck, a piston is broken and all sorts of other terrible stuff. It could even be that a slug of the foam air inlet muffler is hung under a valve. The foam covered cone is there to catch the big pieces and the foam is there to silence the intake air noise. If any of the foam is gone, get rid of the rest of it. The engine will run amazingly well on one cylinder. There will be a considerable power loss. If you try to get more from the one good cylinder, it doesn't have the power to give more so your attempt will result in overfueling, hence black smoke.  Coking of the exhaust elbow is also a good possibility. If a chunk of coke dislodged and couldn't pass through the remaining hole, the effect could be an instantaneous loss of power. I'm sure we are all interested to know what you find.