[Alberg30] gas leak from carburetor

[J Bergquist]

Dear Albergers,

I have a gas leak. I thought I would be able to fix it myself, but I am pretty stumped at this point. My atomic4 has an early model block with a late model carburetor and ignition system. I have a diaphragm fuel pump that I did not rebuild or otherwise monkey with when I had the engine removed for the stuffing box service this spring. I kind of wish I had. 

I DID rebuild the carburetor, including having it cleaned thoroughly by a friend who has an ultrasonic parts washer (very cool machine). After reassembly and installation of the engine, when I hooked up the fuel lines and opened the valves, everything seemed fine. No gas leaking. However I was not able to get the engine running due to operator error in assembling the ignition system. ;-)

Once I got the ignition system fixed, the engine seemed to run fine, but I was leaking gas from the carburetor. It was dripping from the drain plug at the bottom of the sediment bowl. Admittedly, I was not sure if a loose plug was the problem because it's a low point and gas would collect there before dripping, so I took the carburetor off for checking. And I discovered that I actually have two drain plugs at the bottom of the bowl and one of them was indeed not screwed in all the way (although it did not seem particularly loose). I tightened it and the fuel leak seemed to stop (the bowl was still full). So I though the problem was solved, and I happily reinstalled the carburetor, cleaned everything up and gave it a whirl again. It seemed fine and everything remained dry and sweet smelling, until I turned the engine off. Then it started dripping again. This time I was able to feel that the gas was actually leaking down around the sides of the float bowl, so couldn't be comin!
g from the plug(s). It must be either from a crack in the bowl (which I was unable to see, and which seems unlikely since there is no leakage when the engine is running) or from overflow somehow. 

My current theory is that I have some gunk stuck in the seat of the float valve and it is not shutting off the gas line running into the float bowl and so gas is running down the line and into the float bowl (however, I am currently closing the gas line valve every time I turn off the engine to prevent this, which seems to work). This doesn't occur when the engine is running because the gas level in the float bowl remains consistently lower since the engine is consuming gasoline as it flows into the bowl. I have also been told that the two mating surfaces of the carburetor can tend to get warped and that perhaps the top and bottom half are not mating sufficiently well to get a good seal at the gasket. I guess this could also be the problem. Does anybody else have any other ideas what might be causing this kind of gas leak? Has anybody had a cracked float bowl before? 

I know it's very dangerous, and I am doing my very best to get it fixed ASAP.

Thanks for all the great advice!

J Bergquist
Calliope #287
+---------------------------------------------------------------+
 |  Boatowners Mechanical And Electrical Manual by Nigel Calder  |
 | http://www.amazon.com/exec/obidos/ASIN/007009618X/alberg30-20 |
 +---------------------------------------------------------------+

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