Black Smoke & Low RPM w/Yanmar

[Bert Kinyon]

After clearing obstructions from my raw water input into my exhaust elbow I now have plenty of water going through my exhaust system. Now, test running at high rpm under load while tied to the dock I notice black exhaust. My RPM's have been falling lately as well.I'm assuming my injectors are fouled a bit.Am I assuming correctly?Any suggestions for a good fuel additive to clean the injectors?

 

[hp]

check out

check for a fuel leak! Sounds like you could be getting air in the fuel system

 

[Bert Kinyon]

Black smoke problem was probably the load

A freind of mine may have just answered my question.I need to load test my engine away from the dock. A diesel will emit black smoke when it is under a more then usual load. Such as being tied up to a dock and not being able to get any water moving into the propeller (lessening the load). Being attached to the dock means my engine is working harder then it normally should. Just like a diesel truck pulling a load up hill it natually will emit black smoke which will go away when the engine is operating on a level highway.I'm going to load test the engine out on the water and see what happens then (any excuse to go for a ride eh??).Tnx,

 

[Tim Leighton]

MIXING ELBOW

Bert: You mentioned that you cleaned the raw water input fitting to the mixing elbow but not whether you cleaned the mixing elbow itself. You should NOT be getting lots of black smoke from your exhaust, even under high RPM at the dock. Even when you see good water flow the mixing elbow may be at least partially clogged (trust me, I KNOW!!@#$#). If you haven't done so, take the mixing elbow off and give it a good cleaning (I use a mild Muriatic Acid solution). It is a pain in the A-- to take the darn thing off, but should be part of your periodic maintenance schedule (it is mine...every 2-3 years). Talked to a Yanmar mechanic yesterday about this very same problem (low RPM) and he agreed that the most likely cause was restricted raw water flow, followed by injector problmens and air in the fuel. Good luck. Let us know what you find!Tim L. (S/V "TIDE")