I noticed gas flowing out of the carb behind the flame arrestor and down into the bilge....had it rebuilt in hopes that this would fix the problem...no such luck. The floats seem to be fine and the needle seat valve seems to be ok. When I reinstalled the carb, the engine started up and ran fine. I shut it off and engaged the choke to see if the problem was solved and I saw the same gas discharge again. I took off the flame arrestor and looked into the throat where the choke is and noticed that the gas was coming out in gushes. Has anyone else experienced this condition?
Steven, ALLERON, #332
Alleron has experienced a similar carb leaking problem in the past. I simply keep the fuel valve shut off unless I am actually running the engine (never does it when the engine is running). Ive cleaned the carb more times than I can count in the past year, and have just gotten used to things. I also keep a reminder clipped to the ignition key to turn off the gas.... (and have trained my girlfriend to remind me to check such things when she is there). Sorry I cant offer you a solution (I think your right about gravity/sticking float being a factor), but at least you wont feel alone!
Lee, LASTOCHKA, #273
I had a Zenith straight-style carburetor on my A4 and had a similar problem. I rebuilt the carb and found that there was a gap between the bowl and the top of the carb on the intake (flame arrestor) side that the gasket would not close. I asked around and the consensus among the mechanics here was to seal the gap with silicone. Not my idea of a "good and safe" fix but a fix nonetheless. I asked Don Moyer about this problem and he said that this warping was a design fault of that carburetor and Zenith had redesigned the carburetor with a 5th screw at exactly that place where the gap was. Don was nice enough to offer me a permanent fix. 130 dollars later I had a new carb. Another place you might look for leakage is around the carb gasoline supply inlet. If the inlet fitting is overtightened the casting will fail. After smelling gasoline around my engine and knowing what gasoline fumes can do to a good sailing trip (or life for that matter) I have installed a manual shutoff at the carb and a 12V solenoid valve just upstream of the manual shutoff.
Rob Squire, HEAD OVER HEELS, #96
For you guys with carb warping problems, I have had trouble with silicon as a gasket material and gasoline. Seems those two are really not very good bedfellows. Permatex makes a lot of products that are more compatible. Marine-Tex is an outstanding product to reform a piece that will be
impermeable to gasoline. Be sure to use a no stick surface on one of the pieces, so you can get it apart later. I rebuilt the fuel tank on my Triton 9 years ago with Marine-Tex and absolutely no problems. I more recently rebuilt a fuel tank on an old ski boat, and again, the Marine-Tex proved to be a good solution to resealing the holes.
I bought a brand new carb - and the same thing would happen occasionally. This was the single biggest reason I replaced the engine. I actually considered replacing the carb and extending the manifold to a downdraft and using a small "SU" carb. I think what happens is the fuel tank is higher than the carb. The fuel pump allows flow even when not pumping and the fuel float sticks low. The gas just gravity drains into the bilge. I helped my problem of dumping gas into the bilge by placing a 12v valve in the gas line that shuts off when engine is not running. Then if problem manifests just hit fuel bowl lightly and should be okay again.
Gary Everingham, Protege
Protege has an electric pump and it runs continuous at greater than 5 PSI without leaking from the carb. It sounds like the float is stuck in the down position or the seat / needle valve is not aligned or is missing or the float is not adjusted to the correct height. Check all these, one or more is the cause.
Either your carburetor has been incorrectly rebuilt or you are installing it at a very bad angle (unlikely). The float needle is either set wrong or is not working. Maybe there is dirt under the needle valve (?) preventing it from closing. Whatever the cause it does not rely on the engine running or is anything to do with the fuel pump. Fix this before you go any further!! You do not want fuel leaking into the bilges, vent fan or not.
Walton, Galatea, #330
Indirectly related- We had an experience where the motor repeatedly stalled after one minute of running. The problem was traced to a pin hole leak in the carburetor float, which prevented it from turning off the fuel flow, therefore flooding the engine. There are no carburetor inter links with oil pressure or fuel pump or anything.
Chuck Millar, Cadenza, #616
I just had my carburetor rebuilt. When I put it back in the boat and turn on the ignition (without runningthe starter), the fuel pump clicks for a while as it fills up the float chamber, and then gas starts to pour out by the flame arrester. I previously installed an inline pressure regulator between the pump and the carb that I have set to 3 PSI. I had the impression that I could just run the fuel pump at this pressure and after it filled the float bowl the pump would either stop or at least no gas would make it through the float valve. Am I wrong about this? Is that why there's supposed to be a safety switch guaranteeing not only that the fuel pump won't operate unless the starter is running but also that the engine has to reach a certain minimum oil pressure?