"2007 90hp 2 stroke that likes to sputter when I accelerate. Usually between 3000 and 5000rpm. I thought I had the problem licked by adding dry gas to the tank.... Problem stopped for a few weeks, problem has returned. Is it Ethanol? Fuel-Water Filter? HELP! My local dealer has not been much help w/this motor, it is almost out of warranty. SUGGESTIONS greatly appreciated....."