Where does the water come from? Ethanol can draw moisture out of the air through the fuel-tank vent, enough to cause trouble if left in the tank too long. What's more, ethanol will separate from the gasoline on its own over two or three months, even if no water is present, again putting the engine at risk if the pure juice gets into the fuel lines. When running on E10, it's wise to patronize marinas with lots of business, so the gasoline in their tanks is always fresh.
These problems aren't difficult to solve. First, use your boat frequently, so there's always fresh gasoline in the tanks. When storing her, leave the tanks empty, and refill with fresh gasoline when you recommission. (Check with your boatyard for its requirements on this.) Finally, and maybe most important, always use a non-alcohol-based additive to preserve the fuel, like Star brite's Startron. The company claims it will stabilize E10 gasoline for at least one year. Gold Eagle's Sta-Bil is another good choice.
So in the end there's no need to panic over ethanol. Just follow a few simple procedures, and you—and your boat—should be happy with the new, cleaner-burning, more environmentally friendly fuel.
U.S. Department of Energy
This article originally appeared in the January 2007 issue of Power & Motoryacht magazine.