Many concerns are focused on the increased use of ethanol in the nation's fuel supply, especially the effects of higher-level ethanol blends on marine engines. Mixtures above E-10 (ten percent ethanol) gum up or compromise fuel tanks, fuel lines, gaskets, or cause safety problems with marine engines, such as over-heating.
Boat builders use five types of materials to fabricate fuel tanks, two of which are aluminum and fiberglass. Of the 18 million boats currently in operation, many millions utilize aluminum fuel tanks and fewer than one million use fiberglass tanks. The data clearly indicate that the increased use of ethanol in gasoline poses significant safety and durability issues for these types of fuel tanks. Aluminum is a highly conductive metal that relies on an oxide layer for its corrosion protection properties. Low levels of ethanol, such as E10, are usually not a problem in aluminum tanks because the oxide layer provides a good measure of protection. But because ethanol absorbs water, higher amounts of ethanol in fuel equate to higher amounts of water in fuel tanks. This, naturally, causes corrosion, which itself creates particulate matter that then clogs fuel filters, fuel systems, and damages engine components. Older boat models typically have fiberglass fuel tanks, for which there is strong evidence that even relatively low amounts of ethanol can cause serious engine damage.
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