Ethanol additive can gum up boat engines

By Jesse Husid - July 13, 2006

A change in gasoline additives has caused problems for pleasure boat owners, especially those whose boats are powered by outboard motors, according to two Island mechanics familiar with outboards and the change in fuel composition.

Steve Swartwood of Herring Creek Marine in Edgartown and Don Edgar of Don Edgar Marine in Oak Bluffs said this week that they've heard about more problems than they've seen, but they described the complications facing boat owners, especially those with fiberglass fuel tanks, now that ethanol has replaced MBTE in gasoline sold in Massachusetts.

E-10 gasoline, which is now being used nationwide, may be better for the environment, but many boat engines are suffering as a result. E-10, commonly referred to as gasohol, is a combination of 90 percent gasoline and 10 percent ethanol, an alcohol produced from corn and other grains. First appearing in boat fuel 10 years ago in the Great Lakes region, ethanol was brought to New York last year and was introduced in Massachusetts in May. Ethanol is gradually replacing methyl tertiary butyl ether (MTBE), a toxic additive that helps oxygenate gas and reduces emissions.

The switch was a result of the Federal Energy Policy Act of 2005, which did not grant MTBE producers the limited liability protection they wanted, in light of findings by city governments nationwide that MTBE had found its way into drinking water supplies, according to the National Council for Science and Environment. The Clean Air Act of 1990 required oxygenates in gasoline in areas with poor air quality, and ethanol is believed to be a safer replacement. Ethanol is designed to reduce toxic exhaust emissions, enhance engine performance, increase the octane level in unleaded gasoline, and keep engines cleaner, while reducing dependency on oil, as noted by the American Coalition for Ethanol.

But E-10, although widely used in cars, can have negative effects on boat engines, according to information provided by Falmouth Marine. Fiberglass fuel tanks in boats are particularly susceptible. As a solvent, ethanol dissolves resin in the fuel tank, which affixes itself to engine intake valves, which can stick, causing engine damage. In addition, the corrosion that ethanol can cause in older tanks can cause engine damage, and in some cases, gas leaks. Boat owners with fiberglass tanks should contact the manufacturer to see if their fuel tank is ethanol compliant or resistant. If it is ethanol resistant, manufacturers recommend adding a vapor detector to detect fuel leaks, if installing a new fuel tank is not an option.

As a solvent, ethanol is helpful in that it dissolves varnish and deposits that have built up in a fuel tank, something regular gasoline doesn't do.

But, according to Mr. Swartwood, "That can clog up fuel filters, so it's important to be changing the filters." He recommends that boaters using E-10 should carry spare filters and know how to change them.

The second common problem with ethanol is that it absorbs water. Ethanol does not naturally mix with gasoline but is very absorbent. The combination of ethanol, water, and other elements in the fuel create sludge and other corrosive compounds, according to the National Marine Manufacturers Association web site, NMMA.org. In addition, when the ethanol absorbs enough water (about three quarters of an ounce or more per gallon, according to Falmouth Marine's information), the ethanol phases out of the E-10 mixture, as does the octane, creating two stratified layers, with the gasoline at the top. If the fuel lines are at the bottom of the tank, they will take in the alcohol and water first, not the gasoline, which will cause stalling and complications starting the engine.

"The best way to solve that is to get the tank cleaned and all the water sucked out," said Mr. Edgar. Mr. Edgar recently had a disgruntled boater come to him complaining about trouble starting his engine. Mr. Edgar found a "jelly-like blob" clogging the filter, upon inspecting the fuel line, a result of the absorbed water and deposits from inside the tank. Fuel-water separators may also help with small amounts of water. He recommends that boaters use up as much of the MTBE gasoline in their tanks as possible before filling up with E-10, as they do not mix well.

Both Mr. Swartwood and Mr. Edgar have heard of a lot more ethanol-related boat engine problems than they have seen. "I've only seen a few more engine problems this year than in other years," said Mr. Edgar, while Mr. Swartwood says he hasn't had any problems with ethanol.