Boaters Urged to Avoid E15 Gas this Season

With the EPA’s recent decision to allow the use of gasoline with up to 15% ethanol (E15) in 2001 and newer model cars and trucks, the nation’s leading boater-advocacy group is urging trailerboaters to be vigilant when fueling up at their local gas station. While E15 could be fine for the tow vehicle, BoatUS warns that it’s not good—nor authorized by the EPA—for use in boats. A strong solvent, ethanol has been known to degrade marine fuel systems, damage engines, create safety risks and lead to expensive repairs. The EPA intends to put a warning on gas pumps carrying E15 via a small label (the exact wording has yet to be determined). The following are a few of the problems caused by E15:


In addition to the hydrogen and carbon found in regular gasoline, ethanol contains oxygen, which means that less air is needed for combustion. Too much oxygen in the fuel/air mix results in “enleanment”. While most cars and trucks on the road today have closed-loop systems that adjust to prevent enleanment, most boats have open-loop systems, adding a greater risk of heat-related damage to the engine with E15.

Compatibility Questions:

Many components on a boat come in contact with ethanol-laden gasoline, including fuel lines, fuel tanks, fuel pumps, fuel injectors, carburetors, pressure regulators, valves, o-rings, and gaskets. The compatibility of these components with any blend greater than E10 is currently unknown. The failure of only one of these components in your engine could lead to failure or, worse, a fire or explosion.

Phase Separation:

Phase separation occurs when gas becomes over-saturated with water (ethanol bonds readily with water molecules), causing the water/ethanol mixture to separate from the gasoline and settle to the bottom of the tank, where the engine’s fuel pickup is located. Once phase separation has occurred, the only remedy is to completely empty the entire tank. Fuel additives do not restore phase-separated gas back to its original state.

Warranty Issues:

If your engine or fuel system is damaged by E15 gas, the cost of repair or replacement will not be covered by the warranty. Marine engines are only warranted for use with up to 10% (E10) ethanol.

For more information on ethanol

BoatUS Ethanol Information

To ask a question or see a discussion on where to find ethanol-free gas at marinas:

BoatUS Ethanol Message Board & Forum

How are you going to deal with your engine’s gas this season?

Please advise us in the comments box below.