Gas in the bilge

[Pipe_Dream]

Make sure you don't have any leaks where the filler hose enters or the feeder hose leaves the tank. If your tank has a sending unit for a gauge you could have a leak there as well. Any of these you should be able to see if you remove the cover, or through access holes if your cover has them.

You can try to pressure test it but imho the results are not definitive.

If you can eliminate the top leak posibilities, the odds are pretty good you have a leak in your tank. I had two holes in mine due to corrosion.
http://www.wellcraftv20.com/gallery/...mp;id=P7300409
http://www.wellcraftv20.com/gallery/...mp;id=P7300411

Good luck and let us know what you find.