I have a 2004 Sportster LE DI. The past few times that I have been out I have had intermittent issues going past 5000 RPM. The boat generally starts out fine with the full power range, but if I cruise around slowly (around 4000 RPM) I sometimes have issues where I can only get 5000 RPM if I go WOT.

At first I suspected a throttle issue, since I get 5000 RPM at half throttle and it remains at 5000 RPM at full throttle. But, I do hear an audible difference between half throttle and full throttle, jut no real RPM difference or speed difference. I'm not sure if I hear some sort of sputtering or popping form the engine.

Other times I have driven the boat hard without issues. any ideas?