I don't think most non-boaters understand how much gas these boats can take. Last week twice when I went to the gas dock the guy at the pump said "you've already got 10 gallons" like hey I think you're about full- should have seen his face when I said "she'll take at least 30" another one said "you sure you want to keep going?" when I was at 20 gallons, and those are marina workers. I have a friend who rode pretty regularly with me last year and finally he offered 5 bucks for gas. I told him thanks but no thanks- well now this year he has his own boat and was shocked after about a week at how much it takes.

you could pull the old "oops I forgot to fill it up after our last trip, wanna go past the gas station/gas dock with me on the way out?" trick. If he sees you drop $100 in the tank he might get the picture.