The top engineer at Mercury Marine testified before Congress last week about the dangers of ethanol in gasoline to the recreational boating industry.

Tim Reid, Mercury’s director of engine design and development, warned members of the House Science Committee’s Subcommittee on Energy and Oversight about the harmful effects of fuel with more than 10 percent blended ethanol on small marine engines.

Reid cited two studies — one by Volvo Penta and the other by Mercury, both in association with the Department of Energy and the National Renewable Energy Laboratory, according to a statement from the National Marine Manufacturers Association.

The studies tested the effects of 15 percent blended ethanol, or E15, on performance, emissions and durability. In all cases E15 had catastrophic effects, leading to increased emissions, deterioration and in most cases complete engine failure. Reid warned that the use of E15 is not only dangerous for engines, but also creates a safety risk for the boaters who rely on them.

“E15 creates a higher probability of phase separation with water in the tank fuel, resulting in a greater chance of disabling the boat engines and stranding a boater out on the open water,” Reid told the subcommittee.

Modern marine engines are only certified to run on fuel with 10 percent blended ethanol (E10) or less. Engines made before 1990 are not certified to use any fuel blended with ethanol.

The Renewable Fuel Standard sets the levels of ethanol to be blended into the overall fuel supply at flat numbers and didn’t account for the drop in fuel consumption that has occurred. That means that to comply with the RFS, ethanol levels would have to exceed what some call the “blend wall,” or the levels that most engines could handle.

Reid reminded Congress of the incompatibility between E15 and the still numerous older engines in the fleet, warning of the dangers misfueling poses to those boaters and their engines. Reid also rebutted assertions that fuel with higher ethanol blends decreased emissions, saying that the use of E15 caused engines to run hotter, increasing the output of nitrogen oxides and hydrocarbons.

“The absurdity of it all is that by using higher ethanol blends to achieve the mandates of the RFS, we are actually increasing emissions and lowering efficiency,” Reid said.