In the past year there's been a lot of worry among boaters about the ill effects of soon-to-be-universal E10 ethanol-blended gasoline. Depending on who's talking, the changeover from gasoline laced with methyl tertiary-butyl ether (MTBE) is a small problem, a catastrophe of biblical proportions, or somewhere in between. But what's the truth? Should we panic? Here's what you need to know.
E10 is a blend of unleaded gasoline and ethanol, no more than ten percent by volume of the latter. Ethanol—basically grain alcohol—replaces MTBE as an oxygenate to reduce carbon monoxide emissions. It's better for the environment and healthier for folks than MTBE, a known carcinogen.
From Out in the Field Into Your Fuel Tank
Burning ethanol for fuel isn't a new idea. According to the U.S. Department of Energy (DOE), Henry Ford's first car, the 1896 Quadricycle, ran on pure ethanol; the first Model T could run on ethanol, gasoline, or a combination of the two. Today one out of every eight gallons of gasoline sold in the United States contains ethanol, says the DOE, most of it E10. You're probably burning it in your car already and maybe in your gasoline-powered boat, too.
Any gasoline engine manufactured in the past 15 years will run on E10. Today Honda, Kawasaki, Mercury, OMC, Volvo Penta, and Yamaha, among others, approve the use of E10 unleaded gasoline for their engines. If your engine is older, check with its manufacturer for specific advice, and keep an eye out for leaks in fuel lines and connectors, as ethanol and other alcohols will degrade rubber. Thus 15-year-old rubber fuel hoses might be damaged by ethanol—but if your fuel lines are that old, they're overdue for replacement anyway.
So where did all those horror stories come from? The problem isn't with the E10 itself, but the effect ethanol has on gasoline tanks. Ethanol is a solvent that will dissolve varnish, sludge, and other crud inside the tank and fuel lines—basically it will clean them. The fuel filters on many boats let the tiny contaminants pass through to the engine, where they can clog injectors and accelerate wear. The solution is simple: Replace your conventional fuel filter with a 10-micron water separator designed for ethanol. Most experts predict the filters will clog frequently when you first switch to E10, so carry spare elements. Once all the debris has been strained out, the elements should live a normal life span.
But for folks with fiberglass tanks, there's another problem. Ethanol also attacks most polyester resins, weakening the tank over several years' time and maybe even causing leaks. Dissolved components in the gasoline, primarily styrene, can also damage the engine. Check with your boat's manufacturer to find out if your tanks were built with ethanol-resistant resin. If not, the safest thing is to replace them with ones made of stainless steel or even plastic. Yeah, this can be expensive and complicated—so maybe you can use this as an excuse to trade in the old barge for a new one. The folks at Volvo Penta advise those with aluminum tanks to beware, too: Moisture in the E10 could cause corrosion of the metal, they say, resulting in the eroded material clogging fuel filters and damaging injectors, carburetors, and other components.
There are also issues with water contamination. Ethanol can absorb ten times as much water as MTBE can and carry it through the engine to be burned away. However, if the concentration exceeds the fuel's saturation point (about 0.5 percent by volume), the process reverses: The water pulls the ethanol out of the E10. Engineers call this phase separation. The ethanol-water mix sinks under the pure gasoline, which is now of slightly lower octane (ethanol boosts the octane of E10 about three points higher than the gasoline alone). Low octane could cause the engine to run poorly, burn more gasoline, and emit more pollutants. If enough of the ethanol-water mix collects under the gasoline, it can be drawn into the engine. We all know engines don't run so well on water, but pure ethanol can also be damaging.
This article originally appeared in the January 2007 issue of Power & Motoryacht magazine.