Ok, so I was wrong about it being a fuel problem.

What I did was to coat each plug wire terminal, both ends, heavily with dielectric grease. That'll keep water out of the sockets and prevent corrosion. You can find it at any auto parts store.
I also keep a can of WD-40 on board to spray on the ignition system and under/inside the cap if I find moisture. WD-40 displaces water.