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How does ethanol affect your boat’s performance?

gas canStarting in 2007, gasoline sold in Ontario must contain a minimum of five per cent ethanol, an amount scheduled to rise to 10 per cent in 2010. The move has some cottagers wondering if their old outboards can swallow this new fuel.

Ethanol is simply a form of alcohol, produced through the fermentation of sugar or converted starch, usually from corn. Blended with gasoline, it provides a sustainable replacement for fossil fuel and also boosts octane, helping to create cleaner-burning combustion without the need for harmful additives.

The downside is ethanol’s affinity for water absorption, which is greater than that of unblended gasoline. “Water in the fuel is always something to be conscious of in a marine environment,” says Honda Canada technical analyst Bill Rising, “mainly due to the long storage periods and the way fuel is stored – often in metal tanks – and temperature fluctations that occur when the boat sits unused during the week, causing condensation to form.”

It’s best to avoid mixing ethanol-blend gas with older gas, says Frank Kelley, fuels and lubricant specialist at Mercury Marine. The first time you introduce blended gas to your boat, check that the tank is completely dry and clean; any residue of water and debris will be more soluble in ethanol gas, and a buildup “could cause filter plugging or damage to your engine,” Kelley says.

A special note to cottagers who have older outboards: The rubber compound of hoses in fuel systems built before 1991 can deteriorate from exposure to ethanol-blend gas. Kelley advises that boaters make frequent inspections of their fuel lines for any signs of leaking, softening, hardening, swelling, or corrosion, and replace the hoses if necessary.

- Bruce Reeve

Originally published in the May 2007 issue of Cottage Life magazine.

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