Gasoline in exhaust

[RedBaron]

I noticed some gas in my exhaust on leaving the dock. What might be the cause, and what can I do about it?

[Don Moyer]

I think we'll need a bit more information:

1) Could you elaborate more on your observation? Is raw fuel actually running out of the exhaust, or are you seeing specks of fuel on the water?

2) Is the engine running OK otherwise? Did the problem just start?

3) Was any maintenance performed on the engine lately?

4) Are you seeing or smelling gasoline anywhere else (like in the oil)?

Best regards,

Don Moyer

[RedBaron]

gasoline in exhaust

Bill, to reply to your questions:
1) I noticed only specks of gasoline on the surface of the water.
2) & 3) The gas tank was removed and cleaned recently, an electronic ignition was installed. Before that, a failure at the cockput end of the gear shift required reworking that linkage and the reverse/forward gear was adjusted, but perhaps not perfectly, and the throttle doesn't seem to act the way it once did. The latter could be due to the fact that the transmission isn't adjusted as it should be, and, as a result, the thrust from the prop isn't either. (All on a Pearson 35.)
4) I can't tell whether the smell of gasoline is from the oil or not, but very recently I get a smell of gas when I never used to. (I have had an electric fuel pump for many years, and it has not given me any problems. I have an additional fuel shut-off valve just after the fuel pump, and I run the fuel out of the carburetor before shutting the engine off, so that I don't build up any deposits in the carb.)
[Long answers to short questions!]

[RedBaron]

gasoline in exhaust

My apologies to Don for calling him Bill.

[Don Moyer]

No problem, I've been called much worse. Besides, my best friend is named Bill, so I was sort of flattered.

Thanks for the additional details. Based on the fact that you have an unexplained smell of gasoline recently, it may well be that your float valve in the carburetor is not closing completely and fuel is collecting in the throat of your carburetor. You can check for this condition by removing your flame arrestor (housing and all) and inspecting the throat of your carburetor, both while your engine is running and when it is not. If you observe any raw gasoline in the bottom of the intake throat, you'll probably have to remove the carburetor and disassemble it for a good cleaning. The best way to cure a float valve leak is to take a piece of 3/16" wooden dowel (with the end ground to a blunt point) and work it around and around, pressing it against the brass seat of the valve.

The other possible scenario would be an ignition problem in one or two cylinders, but if that were the case, I would expect you to have a rough running engine, which you're not reporting.

Good luck,

Don