I am new to the pontoon world. I recently purchased a 2075GL with a 115 Yamaha. My prop is 13p. Having issues over 4k rpms. Prop will spoil up to 5900 rpms, but gain speed over 20mph. Anyone having the same issues? Sometimes rpms will just sky rocket when power is applied over 4k and the boat seems to lose traction, for lack of a better word.