I have a 2011 GLI that has a 115 Merc with a 2208 15 prop and two 25in pontoons. I am running 22mph GPS and turning 6400 RPM's according to the Tach. That is with 2 adults and full tank of fuel. It seems the RPM's are to high and was wondering if this is the best speed that I can expect. I was looking at the Spitfire 4 blade props in 17 pitch to lower the RPM's.Open to any suggestions and help. Thank you for any input and help.