In this month’s issue of “Practical Sailor” there is an article on ethanol fuels and the impact on fuel systems. This article is timely in light of the refinery fire in Whiting and the Department of Energy’s relaxing of pressure standards allowing the suspension of summer blended fuels.
When you fill your your portable fuel tank the temperature of that fuel is important in how much it will expand as it is stored on your boat as temperatures rise. The concentration of ethanol in the fuel has a direct impact on the amount of expansion that occurs in the tank. The example used in the article is filling a portable tank with non-ethanol fuel at 55 degrees F ( fuel stored underground) and it warms to 90 degrees F increases tank pressure by 2-3 psi. With E10 the pressure would increase to 6 psi. If the tank with E10 is left in the sun and the temperature rises to 120 degrees F the pressure would increase to 20 psi where the tank with non-ethanol fuel would be about 11 psi. Plastic tanks and their components are leak tested at 10 psi.
During summer if the tank reaches 120 degrees F the fittings, connectors and fuel line could begin to leak.. Plastic tanks also weaken over time. Depending on the UV inhibitors used by the tank manufacturer the tank will lose about 6-8 percent of its tensile strength each year if it is exposed to the sun. In order to minimize this deterioration fuel tanks they should be kept out of the sun. If your tank is exposed to the sun it should be replaced after 5 years. If your tank is 8 years old it should be inspected for bleaching, checking and tiny cracks. Any one of these is a reason to replace your fuel tank.
The article goes on to say that ethanol in and of itself is not that corrosive but the the water it absorbs pits the bottom of the fuel bowl, creates aluminum oxide that ends up plugging the carburetor jets. To keep water out of the fuel make sure your tank eats are in good condition and the vent is closed when the engine is not in use. The fuel should be treated with an anticorrosion additive like Biobor EB or Stabile 360 Marine.
Other notes in the article are the if you have an older motor and it stumbles at full throttle you may be seeing the first signs of fuel line narrowing. Another reason for stumbling at full throttle are worn connectors. This can be diagnosed by pumping up the fuel primer bulb hard and will stay that way as long as you keep pumping. This can be an indicator of a weakened fuel line.
Hope this I helpful.