I have a Bass Tracker with a 40 HP Johnson Motor J40ELCD. The Motor will not run over 2000 RPM with Full Throttle(10 MPH?). I can get the Boat up to 30 MPH(3500 RPM) if I hold the Primer Switch in. If I let the Switch out the Motor immediately slows down. Can someone tell me What is wrong. I have checked for gas leaks and see none. I have even changed the gas primer bulb and hose.