SE10: Trouble for marine engines?
by Ann Backus

Orbital rated all (effects) at six or above with fuel leaks rated at 9 and throttle sticking at 10 (very severe).

Ann Backus, MS is an Instructor in Occupational Health at Harvard School of Public Health, 665 Huntington Ave., Boston MA 02115, 617/432-3327, abackus@hohp.harvard.edu

As the boating public launched another summer of recreational boating and the commercial fishermen geared up for the summer fishing season, reports of problems small and large surfaced in newspapers. Glenn Adams, an Associated Press Writer, produced a July 4th column for the New York Times titled "New England boaters wary of ethanol. Across the continent in British Columbia, Robert Barron of Canwest News Service, wrote an article titled "Ethanol-blended fuel can cause headaches for boat owners."

Engine problems are increasing in the marine environment as ethanol-blended fuels (one of which is graded E10), developed to meet EPA regulations for improved air quality and reduce dependence on oil, are becoming available across the country, including on the coasts, quite distant from the corn belt.

While E10, a blend of 90% gasoline and 10% ethanol, poses few problems for automobiles because they have been manufactured for some time with blended and reformulated fuels in mind, gasoline-running marine engines, both outboards and inboard/outboards are potentially at risk.

A comprehensive 2002 study by Orbital Engine Company for Environment Australia lists the common effects that can result from using E10 fuel. Their list matches the experience of boat owners in New England, namely, lack of power, leaking fuel, sticky throttle, and poor engine running including poor starting, rough running, unexplained stopping, and seizure. Rating these problems on a scale of 1 to 10, Orbital rated all at six or above with fuel leaks rated at 9 and throttle sticking at 10 (very severe).

Why is E10 causing these problems and what is the "fix"?
The chemical properties of ethanol are responsible for these problems. Check your engine specifications for compatibility with E10 fuel and if possible use fuel that is 100% gasoline – it does still exist especially at marinas. If you use E10 fuel here is what you should know about it.

Ethanol is hydroscopic – mixes easily with water. Ethanol will mix with any water in the gasoline, causing a phase separation such that one portion of the fuel will be gasoline and the other a water/ethanol mix. Phase separation can affect starting, idling, running, power, and can damage engine parts by reducing lubrication.

The vapor pressure of the blend is considerably higher.

The fix: If you cannot locate nonblended gasoline, take measures to keep water out of the fuel tank; leave it full or empty to avoid condensation; and install a water separating fuel filter, available for from $25 to $80 and carry extra filter cartridges on-board.

Ethanol is a solvent. It will dissolve any gunk or gasoline fuel residues in fuel tanks, hoses, carburetor, etc., and deposit gunk particles anywhere that the gas goes, in fuel lines, on spark plugs, fuel nozzles, valves, pistons, rings, fuel filter, etc. Articles on this topic refer to ISDs, intake system deposits – for four stroke engines. The amount of additional deposits with E10 is reported to be on the order of 350 times even when a usual amount of fuel additive is used.

The fix: Avoid using E10 and certainly anything higher than E10, such as E17 or E20. Ask the engine manufacturer about using a fuel additive to reduce deposits and be aware that considerably more fuel additive may have to be used than would be necessary with unblended gasoline, given the chemical interaction between ethanol and the additive.

Ethanol-blended gasoline has a higher vapor pressure than non-blended gasoline. Because of the physico-chemical properties of ethanol in the presence of gasoline, the vapor pressure of the blend is considerably higher – higher than either the vapor pressure of gasoline or ethanol alone. This property is of special concern in aircraft engines because those engines require a hotter burn to achieve lift-off and when airborne are operating at a lower atmospheric pressure.

If the fuel vaporizes in the fuel line, a vapor lock results, and the fuel pump does not receive an adequate amount of fuel to deliver to the carburetor/engine. A vapor lock can be dangerous if it causes the engine to cut-out suddenly, and it will be annoying if the engine baulks and hesitates or doesn't start reliably.

The fix: If you have no alternative to E10 fuel, you may need to increase the richness of the burn; this will deliver more fuel to the carburetor, but will also result in greater fuel consumption.

How can the risks be minimized?
In addition to the "fixes" which, in fact are not guaranteed or the only answer, avoiding other serious problems on board requires additional vigilance and more frequent inspection. The solvent property may dissolve rubber hoses. Additional checking of fuel lines by finger inspection for cracks, weak walls, and tiny leaks is very important. A ruptured fuel line presents a serious fire hazard. Also we hear reports that the integrity of fiberglass is also at risk. Check your bilge thoroughly before and after each trip to ensure that fuel is not leaking into the bilge. Take immediate measures to find and solve the problem if the smell of gasoline is stronger than you are used to. Change your fuel filter more often – in fact if you are using E10, you should consider installing a water separating fuel filter.

Acknowledgement for material presented in this article goes to Richard Hiscock, inveterate clipper of commercial fishing safety news around the country, and two reports obtained from the web: 1) Report to Environment Australia. A Technical Assessment of E10 and E20 Petrol Ethanol Blends Applied to Non-Automotive Engines. Failure Mode and Effects Analysis of Engine Function and Component Design for Mercury Marine 15hp Outboard and Stihl FS45 Line-Trimmer Engines. Orbital Engine Company. Nov. 2002 and 2)Report to Environment Australia. Market Barriers to the Uptake of Biofuels Study. Marine Outboard Driveability Assessment to Determine Impacts of a 10% and 20% Ethanol Gasoline Fuel Blend on a Small Batch of Engines. Orbital Engine Company. February 2003.