FOND DU LAC, Wis. — Understand upfront that proponents of E-15 gasoline, containing up to 15 percent ethanol, are not pitching the fuel as suitable for marine engines. In fact, it is a violation of federal law to use it for that purpose.
But E-15 is probably coming soon to a pump near you. Suppose you have a brain infarction and fill your boat with the stuff, which is just the push of a button away.
Not a good thing, based on tests concluded in June by Mercury Marine for the U.S. Department of Energy. Two of three outboards run on E-15 in Merc’s standard 300-hour, full-throttle endurance test failed to complete the run and showed severe internal damage, according to David Hilbert, thermodynamic development engineer for Mercury.
A 300-horsepower Verado experienced three damaged exhaust valves near the end of the E-15 run. Hilbert said the damage likely was caused by operating temperatures considerably higher than those recorded in a similar engine run in the same test on ethanol-free gasoline.
And a 200-horse 2.5 EFI 2-stroke in the test had to be shut down after 256 hours because of bearing failure. Hilbert said more testing would be required to determine if ethanol in the fuel caused a reduction in effective lubrication and brought on the failure, but an identical engine run on standard gasoline had no similar issues throughout the 300-hour run.
Martin Peters at Yamaha agreed that E-15 must not be used in any of the company’s outboards, but he reiterates that E-10 is fine for all late-model motors.
“Accidental one-time use of E-15 will not void your Yamaha warranty,” said Peters. “But for sure, it’s not a fuel you would ever put in your boat on purpose.”
Bottom line is that, while E-10 is acceptable as a fuel for all modern outboards, E-15 is not.
Note that the tests involved fresh fuel used immediately. They did not take into account the issues ethanol causes when it sits for weeks or months in a fuel tank and absorbs condensed water. Nor did they consider the accumulation of dissolved solids that might clog a fuel system.
In fact, the best gasoline for your outboard has no ethanol, and some states still allow service stations to stock straight gasoline. In Alabama, for example, gas stations advertising ethanol-free gasoline generate long lines of bass anglers on weekends.
Floridais considering a rule that would allow service stations to sell gasoline without ethanol, thus letting market demand control the amount of ethanol drivers choose to use. The state’s Senate Communications, Energy and Public Utilities Committee recently voted 10-1 to approve SB 238,which would end the ethanol requirement that has been in place since 2008.
Jeff Wasil, engineering tech expert at Evinrude/BRP, said the company has been involved in recent tests of butanol, a biofuel created from fermentation similar to ethanol, but with fewer issues in outboard engines.
“Butanol is much less likely to create phase separation with water in fuel tanks, and it’s not nearly as likely to dissolve varnish and other sediment in tanks and lines,” said Wasil. “Plus, it can be transported by pipeline, just like petroleum fuels, so the cost of getting it to a blending facility will be lower. Ethanol causes corrosion issues in most pipelines.”
Wasil said butanol can be used in higher concentrations (up to 16.1 percent) in gasoline mixes while delivering the same performance as 10 percent ethanol fuels.
“It’s still more expensive to make than ethanol, but improvements in technology are bringing prices down, and several ethanol plants are being converted to butanol,” he said. “We’re likely to see more of this product in the future.”