The National Marine Manufacturers Association (NMMA) released the findings from preliminary evaluations on isobutanol-gasoline blends. According to the report, isobutanol produces no more emissions than pure, EPA-approved test gasoline, while producing 30 percent more energy than ethanol. The evaluations are part of the association’s efforts to explore alternative biofuels in response to the approval of E15 for model year 2001 and newer cars and trucks.

The evaluations tested components, including older fiberglass tanks and engines, during on-the-water testing of inboard, outboard, jet pump and two-stroke outboard engines. Although marine engines are not currently EPA-approved for use with E15, boaters should be cautious of misfueling at the pump as fuel containing more than 10 percent ethanol causes severe damage to boat engines.

According to a report from the U.S. Department of Energy’s Office of Energy Efficiency & Renewable Energy, E15 fuel causes significant problems with outboard, stern drive and inboard marine engines. The report compiled data from two studies that compared E15 fuel and fuel containing zero percent ethanol, and examined exhaust emissions, exhaust gas temperature, torque, power, barometric pressure, air temperature and fuel flow.

Engines using E15 had degraded emissions performance outside of engine certification limits, as well as increased fuel consumption. The engines also showed deterioration in durability tests, with two of the three outboard engines sustaining enough damage to prevent them from completing the test cycle.

The results reinforce concerns that E15 is not a suitable fuel for marine engines. For the complete study results, visit www.nrel.gov.