Black soot from discharge - M25

[jerzyjoe]

I have begun to notice a black discharge from my exhaust upon starting the engine. This does not result in a slick and immediately sinks. So it is not oil. And the engine runs fine. I have seen other posts about a black moustache on the transom but this is different - no moustache. How worried should I be?

Thank you
Jerzyjoe

[Sea Hunt Video]

JerzyJoe:

There are many others with a lot more knowledge than I but I offer the following until the experts post:

Possibly bad or incomplete combustion or bad fuel.

This could be caused by a bad injector.

Insufficient air flow; thus incomplete combustion.

Also, bad quality fuel in the diesel tank.

Your post does not indicate if the "black discharge" is constant or only upon "starting the engine". If only upon starting, and all is good, probably no big deal. It takes "air flow" a minute to catch up to fuel delivery.

My suggestion would be to get a service manual for your specific diesel engine and then go down the list of possible causes starting with the easy, simple and easily accessible and work you way up (or down) to the more difficult and tough to get at.

JMTC. There are real experts on this board who can offer more detailed and focused suggestions.

[csoule13]

Very curious to see how this thread goes. My YSM8 coughing up some black stuff on initial start up. This weekend, I hung a bucket under the transom and caught it to 1) Be a good boater and 2) To figure out what the heck it is. Smelled like charcoal, and was certainly black and gritty. Did not have any look or smell of oil or diesel. Everything from the exhuast manifold to the transom is brand new(the project that ate the summer).