I have a 2013 20 sl with 25" pontoons, and a 90 hp Mercury 4 stroke. I have the factory 13, 3 blade prop that came from the dealer. I have no problem out of the hole, but when it hits about 4200 rpm, the speed does not change up to about 5300, which is where it tops out. Also what is the actual red line for this motor? Everything says 5000-6000?