high back with the m40d have got the motor running good just need to rplace the prop to get the most out of the motor. right now i have a 10.2 diameter with a 13.9 pitch running 4900 rpm at wot need to get closer to 5500 and would like the most top speed i have a choice between 10.375 diameter and 12 or 13 pitch which would be better?
