Maybe it is just good luck, but the fix I did is easier than all of that. My boat vapor locked a couple of times, very aggravating, and I do change the filter every year. (I have the spin-on type.) I started putting Sta-Bil Marine Ethanol treatment in my tank EVERY time I get gas, and have never had another problem. As some of the posts above refer to the ethanol lowering the boiling point of the fuel, the fuel treatment seems to solve this.

I seem to be killing two birds with one stone, no vapor locking, and preventing the harmful effects of running ethanol.