I believe that E-15 is for those "Flex-Fuel" branded cars only.

Most marine manufacturers have said using any ethanol blended fuel will void their warranty on the motors and fuel systems.

Ethanol absorbs moisture (bad) causing phase separation.

Ethanol also removes some of the varnish and deposits in the cylinder heads/valves which then moves around and cruds up everything.

Most importantly (to a cheapskate like me), Ethanol does not contain the same amount of energy per gallon as gasoline, so I'm getting fewer miles/gallon using E10 fuel.

My outboard mechanic said E10 will corrode the aluminum carburetor in a short period of time, and it could eat some of the fuel hose, clogging the filter.

Ethanol should be used for cleaning and drinking