The Boat Owners Association of The United States (BoatUS) has some advice about how best to store a boat with E-10 gasoline (containing 10 percent ethanol) over the winter.
The major headache comes from the fact that ethanol (an alcohol) attracts water. It also absorbs water about 10 times more than regular gasoline. When ethanol can no longer absorb the water, it will “phase separate” from the gasoline. Should phase separation occur, the (water-soaked) ethanol will settle to the bottom of the tank, which is where the engine’s fuel system pick-up is located, BoatUS warned.
Once too much water has entered the tank and the gas has begun to phase separate, no additive will return the fuel to its original state. The only solution to phase-separated gas is to have a professional drain the tank.
The key is prevention, BoatUS said. Do not leave a tank mostly empty because moist air will enter the tank and the ethanol will absorb the moisture.
The best advice for storing E-10 in your boat’s gas tank over winter, Boat US says, is to keep the tank nearly full. This greatly reduces the volume of moist air that can enter the tank via the fuel tank vent when temperatures fluctuate in the fall and spring. With any fuel, an antioxidant will help keep it fresh during lay-up. Finally, never plug up a fuel tank vent — it creates pressure that could cause dangerous leaks in the fuel system.
For more information go to BoatUS.com/winter.