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Ethanol Storage Questions For My Boat

Getting ready to store your boat for the winter? If you have been buying regular gasoline to run your boat you may have concerns about the ethanol that has been so kindly added to almost all consumer gasoline available. If you listen to the old-timers they will tell you to run the tank down to near empty—the old timers recommendation to leave a tank mostly empty is bad advice, because it could significantly increase the amount of water that gets into the tank. (When enough moisture is attracted through the vent, the ethanol will separate from the gasoline.) An almost Empty tank leaves more space on tank walls for condensation to form. 3. Leaving less gasoline in the tank means there will be less ethanol to absorb the condensation

Some concerns about whether or not ethanol laced gasoline octane will drop faster than regular gasoline? All gasoline will lose octane over time when stored—from my research ethanol mixed gasoline octane drops at the same rate as regular gas so it should not be an issue.

Since E-10 attracts water, is it important to install a water separator to prevent the water reaching the engine? Unlike regular gasoline, which can absorb almost no moisture, E-10 can hold up to ½ percent of water by volume, and the water molecules will dissolve in the fuel. The solubilized water will bypass the water separator and burn harmlessly through the engine in most cases. It’s important that you use a good fuel filter (10-micron) to keep gunk from reaching your engine. Ethanol is a solvent that dissolves resins, rust and dirt that have accumulated on older tank walls. Especially when you first make the transition to ethanol.

Its also a good idea to carry spare filters and a galvanized bucket to store used filters prior to disposal. Even in new engines and tanks, E-10 will sometimes form a mysterious gooey substance that will also clog filters —being stuck on the water because of a cheap item like a spare fuel filter will cost you way more to be towed back into port.

Additives can be used but I have not read any conclusive evidence that they are really effective against fuel degradation so until tnhere is evidence I would save my money.

Unfortunately we have had a shotgun wedding with ethanol in the U.S. and the only way to avoid it in our boats is to seek out the few retailers that sell regular gasoline—which can be pretty pricey and downright inconvenient.

Do your own research before storing your boat, but keeping the tank full seems to be the way to go—maybe you wont have a problem come spring.



  1. Vinzei (Reply) on Sunday 2, 2011

    hi all I read your blog and I think you’re blog will be one of the bests if you keep up the good work!

  2. Bailey (Reply) on Sunday 2, 2011

    I think it would be great if they took ethanol out of the gas for boaters. It would save the economy.