Ethanol Phase Separation is a real problem with any equipment that is used seasonally, especially boats! Avoid Ethanol fuel if possible. When Ethanol fuel sits for long periods of time phase separation occurs and the ethanol sinks to the bottom and pulls in moisture. The photos attached to this post show a fuel sample from the fuel/water separator off an Evinrude E-tec engine that was running poorly and throwing check engine codes and warnings on the system check gauge. The sample on the left clearly shows ethanol and water sludge in the bottom 2/3 of the jar. The jar sitting next to it is a sample of the gas that was recently put in the boats fuel tank. Can you see the difference?
If possible use premium fuel. Premium fuel usually does not contain ethanol. Look at the Ethanol rating on the gas pump when you are refueling.