I've been having a problem fueling my boat. Last season, it worked fine. However, since the beginning of this season, it takes about 20 gallons and then gas comes back out the vent (not the fill pipe). After 4 hours of hard running (when I KNOW it needed more than 20 gallons) I force-fed it an additional 45 gallons, but I can't keep doing that. I never know if my tank is full. Anyone know what might be causing the problem? Oh yeah, there is a screen on the vent, so I don't think bugs could've gotten in.

Jana,
You would be suprised what gets stuck in that vent hose, even with a screen. If you can get to the vent hose easily, check for kinks as well as cleaning it. I had the same problem last year.

If you vent hose has a sag in it, make sure there isn't water in the sag that keeps it from venting.

good luck.