On the Water

Warning: Your Boat Gas Has Changed!

By Jim Crosby

Your boat’s gasoline is changing in many ways that could cause some serious problems. Your attention to this 
detail could at least prevent the serious problems that could lie ahead. 

First and foremost, check the pump before you top off your boat’s gas tank. If a notice on the pump alerts you to 
ethanol being added to the fuel, do not put it in your boat unless your boat manufacturer specifically has stated it is 
suitable for the use of an alcohol additive. I am told that E-10 fuel is being distributed in metro markets like Richmond, Norfolk and the Chesapeake market area. E-10 fuel is gasoline with 10 percent ethanol added. 

The first concern: The most deadly outcome of introducing E-10 fuel into your boat is the potential danger of the corn-based alcohol’s corrosive solvent-like characteristics removing resins and plasticizers from some plastics and rubber materials. Most significantly, it damages the resins in fiberglass fuel tanks. Most common types of epoxy and polyester resin are not ethanol-resistant. 

The second concern: In addition, ethanol acts as a detergent that loosens rust, debris and other gunk inside your tank and fuel lines. So, if it doesn’t dissolve a hole in your gas tank and dump your fuel into the bilge, it will probably clog your filter or gas lines to the point your engine will sputter to a stop. 

The third concern: Ethanol is hygroscopic – it absorbs water and will mix more easily with water than gas. Up to 10% of your fuel could become a water-ethanol mix and the liquid could undergo “phase separation” forming a top layer of pure low-octane gas and a bottom layer of water-saturated ethanol. Since the fuel pickup is located at the bottom of the tank, water contaminated fuel can be sent to your engine to cause it to run badly or not at all. 

This low octane fuel causes problems in four-stroke engines and can cause damage in two- stroke outboards from lean fuel and lack of in-fuel lubrication due to the presence of the water. 

The fourth concern: Ethanol has a short six-week shelf life, and the octane begins to decrease thereafter. While this is a minor concern in a car, this deterioration is a bigger problem in infrequently used boats and worse during winter lay-up. 

Some states have passed legislation that mandates the use of E-10 fuel throughout. This makes it even more important to check the pumps before you fill your boat when traveling. Bills have been introduced in Virginia to accomplish the same thing, however none have been passed into law at this time. 

Eventually, the boating industry will catch up with this trend and produce boats that can cope with the mixing of 
alcohol-based fuels. In the meantime, we need to monitor the fuel we are putting into our current watercraft and stay safe. All combustible fuels are dangerous and we must contain and use them in a safe manner on land or water, but especially on water.