Boston Whaler does not install any fiberglass fuel tanks at the factory. Only aluminum and polyethylene have been used
throughout the years. However, the 10 percent ethanol/fuel mixture will not harm either of those materials.
If your boat has an after-market, above deck, fiberglass fuel tank produced before 1991, you may want to consider replacing it with an updated version. The resins in the older fiberglass fuel tanks may not be compatible with the ethanol, and they can end up being carried into the engine, where severe damage could occur.
Your Mercury engine and Boston Whaler fuel system components will withstand up to 10 percent ethanol content in gasoline, but you should not exceed this amount. Check fuel hoses and fittings for deterioration regularly, and replace as needed.
When storing your boat for long periods of time (two months or more) it's best to remove all fuel from the tank. This is recommended because as the temperature goes up and down in partially full tanks, the void space above the fuel allows air movement that can draw out water through condensation. Ethanol draws that water into the fuel. Significant amounts of water will cause the ethanol and water to separate from the bulk fuel and sink to the bottom of the tank where they can be pumped directly into the fuel system and engine, potentially causing significant problems.
Because of this, it is best to first introduce an ethanol fuel mixture into a dry tank and be careful to keep the water out. Other precautions include keeping the fuel tank full (to prevent condensation) and always having several fuel filters handy (ethanol will act as a cleaner to gummy deposits).
If it is not possible to remove all of the fuel from the tank, the next best option is to keep the tank full and add a Mercury-recommended fuel stabilizer. When starting the boat after a long storage, run the engine for 10 minutes, shut off the fuel supply, and then let the engine run until it stops. Top off the fuel tank and cap any openings to reduce the amount of airflow that could cause condensation.
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