My mechanic says most of the problems occur when switching to ethanol from “pure” gas. The ethanol acts as a solvent, and loosens deposits which get in your fuel system. Ethanol also allows water to be absorbed and burned off instead of separating. He said for optimum results, keep all filters in good shape, top off after using the boat to minimize any place for water to accumulate, and use a good additive. We all know how hard and expensive it is to find non ethanol fuel. Also, you should buy your gas from a station that sells a lot, so it is fresher.