Dirty Exhaust Water

[Ron Mazza]

I have a 1978 Viking 34 with its original Atomic 4. I sail in Toronto. I had the carborator cleaned and installed a new fuel pump this past winter. It starts well, idels smoothly, and runs like a clock. Except, when I started it yesterday evening before our weekly race it spit out a whole lot of black crap that floated on the water in an increasing arc around the back end of the boat. And while it runs, the exhaust water is slightly dark and contains an oily film. It doesn't generate a lot of smoke. Just this black film in the water.

What's going on?

[Dave Neptune]

Ron, any thing else about how it was running during the "spit out". Roughness, misfire, any noises or shaking?

Dave Neptune

[Peter]

Have you checked the oil? Is it milky?

Peter

[Marian Claire]

Over the years I have had a couple of times when I would see chunks of "black crap" at start up from the exhaust. The chunks float on the water. I wonder if it is built up material from the dry side of the exhaust. It happens very infrequently and is one and done.
Dan S/V Marian Claire

[Mo]

The sheen. If it's new just start the engine and remove one spark plug wire at a time. If the engine changes with each wire removal you know that spark plug is firing. If there is no change when you remove one then that plug is not firing. A dead plug would also put a sheen on the water...the film.

If that all checks out then you might want to look at the mixture screw on the carb and back it off a 1/4 turn and see if it's any better. Sometimes corrosion around that port can cause issues as well...if so it can be sometimes difficult to tune it in.

All the best.

[JTG1160]

"It starts well, idels smoothly, and runs like a clock. Except, when I started it yesterday evening before our weekly race it spit out a whole lot of black crap that floated on the water in an increasing arc around the back end of the boat. And while it runs, the exhaust water is slightly dark and contains an oily film. It doesn't generate a lot of smoke. Just this black film in the water."

This is exactly the problem I am now having, were you able to come to any conclusion on the cause? Thx!