Can ethanol-blended fuels affect the performance of traditional carbureted two-stroke outboards?
Two-stroke outboards should experience little or no decrease in performance due to gasoline fuels containing up to 10-percent ethanol when operated according to Mercury’s standard recommendations. When gasoline with ethanol is used for the first time after a fuel changeover from MTBE, the tank must be completely free of water prior to introduction of gasoline with ethanol. Otherwise, phase separation could occur that could cause filter plugging or damage to the engine. (It is probably better for a boat owner to fill the fuel tanks with ethanol fuel for the first time when the tank is low on fuel, but that is not critical. There should be no difficulties if the tank is clean and free from water. If the tank is not free from water, a partial load of fuel will more easily phase separate because with less ethanol in place it takes less water to cause phase separation. The important thing for boaters to concern themselves with is the presence of water in their tanks.) If an engine is a 1990
