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Ethanol: What’s the Real Deal?

You’ve surely noticed it. Ethanol based gasoline. You’ve overheard rumors and uncertainties. Like many, you, too, want to know the straight-up scoop. Is this alcohol-based fuel harmful to our engines or not? We turned to Captain John N. Raguso, Marine Products Editor with The Fisherman and a licensed USCG Master and charter boat skipper with over three decades of offshore experience. Few have as much practical experience in the art & science of boating and fishing than Captain John.


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Phase separation is a serious issue and can result in catastrophic engine complications. Photo: Captain John N. Raguso

A few years back, boaters got a nasty surprise when the formula of their automotive and marine fuel was changed with little fanfare, advance notice, or a real understanding of how it might impact their gasoline engines. Before the introduction of this new fuel, New York, Connecticut and other states sold an MTBE (Methyl Tertiary Butyl Ether) enhanced oxygenated fuel six months out of the year (from October through March) in an effort to cut down on winter smog and air pollution. Environmentalists balked that MTBE was causing some long-term contamination issues with local groundwater and in an effort to solve this environmental dilemma, a 10-percent ethanol additive was chosen as the year-round primary fuel oxygenator for gasoline, birthing the term E-10 fuel. Other northeast and Mid-Atlantic States have jumped on the E-10 fuel bandwagon since then, with the procession working its way down south.

A few years back, boaters got a nasty surprise when the formula of their automotive and marine fuel was changed with little fanfare…

Further cementing ethanol in our boating future, the Energy Independence and Security Act of 2007 was signed into law in December 2007, amending the 2005 Renewable Fuels Standard, requiring that the USA produce 36 billion gallons of renewable fuels annually by 2022. This legislation seized on the thought that renewable fuels reduce foreign oil dependence and greenhouse gas emissions, and provide meaningful economic opportunity in this country for farmers and refiners using a natural, homegrown and earth friendly product (alcohol) that is distilled from corn, putting America firmly on a path toward greater energy stability and sustainability.

Phase Separation
According to Frank Kelley, Mercury’s Fuels and Lubricants Manager, public enemy #1, and the one thing to avoid at all costs when using an ethanol blended gasoline, is the presence of water. Once water gets into the fuel (it can occur via condensation from a half-filled tank, a loose fill cap, deck water and/or spray sneaking into your vent line, or from your fuel supplier, among other ways), you get a nasty situation called phase separation. Only one ounce of water introduced into 100-ounces of E-10 gasoline can cause 10-ounces of ethanol to “separate” from the petroleum base and combine with the water to sit on the bottom of your tank, creating a lethal witch’s brew that will choke your engine. The bad news according to Frank is that once phase separation occurs, it is very difficult to get the ethanol back into the gasoline. “Sooner or later a slug of essentially ethanol and water with little or no gasoline tries to go through the engine.” Bottom line is that no manufacturer’s engines, inboard or outboard, were meant to run on this nasty ethanol and water mix.

An even bigger problem is that running phase-separated gas through your engine can potentially void your warranty, as stated in many new engine warranty manuals. Dean Corbisier, Suzuki Marine Press Manager, mentioned that all Suzuki four-stroke outboards are compatible with the new ethanol-blended gasoline, providing that the ethanol mix is strictly regulated at 10-percent or less. There was an interesting section in the Suzuki manual that mentioned that they, “Highly recommend the use of alcohol-free fuels whenever possible.”

Yet another problem brought to my attention after interviewing various boat mechanics was that there had been an initial surge of carburetor and fuel pump rebuilds, due to the lack of compatibility of the alcohol in the ethanol-blended gasoline compromising the neoprene components of the O-rings, gaskets, diaphragms and seals of older engines that were developed prior to the wholesale distribution of the E-10 fuel.

What Can You Do?

  • Be sure of your fuel source and get some assurance from the supplier that it has no more than a 10-percent ethanol blend.
  • Use a product like ValvTect Ethanol Gasoline Treatment, StarTron (by Starbrite) or E-Zorb (by MDR) to keep moisture in suspension and help prevent phase separation.
  • Use a 10-micron fuel filter with a see-thru bowl and petcock to be able to identify any phase separation and to be able to drain any water out of your system before it gets to your engine.
  • If your boat is more than 10-years old, change your fill, vent and supply lines to the new ethanol/alcohol compatible materials.
  • Keep your boat’s fuel tank full at all times during seasonal use and extended off-season storage to prevent moisture and condensation from working its way into your fuel tank.
  • If you have a boat manufactured prior to 1990 with a fiberglass tank and intend on using E-10 fuel, the best advice is to remove it and replace it with either a poly or aluminum tank.
  • Be sure to tighten your boat’s fuel fill cap after every fill-up.