You
can do a pressure test while the tank is in place, but the results are far from definitive. We pressure tested mine and it seemed to hold . . . until the next time we filled it, and the fumes were overwhelming. :o Holes can be difficult to detect while the tank is in place, what with all the foam around it. Even ones like these:
http://www.wellcraftv20.com/gallery/...mp;id=P7300409
http://www.wellcraftv20.com/gallery/...mp;id=P7300411
Boater, do you smell fumes only when you refuel, or pretty much all the time? Pull the deckplate while you refuel, and watch for leakage around the filler and overflow hoses, as well as the gauge sending unit. If you smell fumes all the time you may have a hole in the tank.