I hope I'm wrong but the last couple times I took the boat out, my tank was
near empty, and both times I was sure I had between 1/3 - 1/2 tank. (40 gal
tank). I trailer it and park in the driveway, so if it's true, it's
happening there. Anyone have any ideas on how to be sure? My wife wants me
to design some elaborate electronic trap with digital video. While not a
great challenge I invision something more low tech like duct tape over the
cap which could never be put back on the same.

Suggestions?

The big bummer is both times I was in the water before I knew it, and had to
go to the gas dock instead of the gas station.
-jeff