I just posted this for the fellow with the low power on a jet drive. Here it is again....
Throttle Control Adjustment
First, with engine off, take off the cover, put in gear (gently), push throttle full open and inspect whether the throttle lever arm (at the cable cam wheel) is up against the stopper. It should be. If not, before adjusting, pull throttle back to idle speed, put shifter in neutral, and follow the cables to the throttle cam wheel (on top of the engine toward the rear) and make sure they are not damaged or kinked.
At the throttle cam wheel, make sure the adjustment nuts are tight. Measure the distance between the adjustment bracket and the end of the cable adjustment threads. The should be 9 mm on both. If not, adjust.
Back to the throttle cam where the lever is located - measure the length from the end of the threaded part back to the adjustment nut - the open side (to your left as you are facing it) should be 14 mm. The close side (to your right) should be 19mm. If not, adjust.
Put back in gear, and push throttle all the way forward. Throttle arm on the cable cam should be up against the stopper. If not, then you likely have a problem with the cable from your throttle control to your engine, which will need to be adjusted or replaced.
If the throttle arm is up against the stopper, then look at there the roller sits in the throttle cam. It looks like a fat inverted "L". The roller should be almost touching the top of the narrow part of the "L". Then pull the throttle lever at your control all the way back, and put the engine in neutral. The roller should now line up with the "V" mark on the foot of the "L." If not, adjust the linkages until the roller does what it is supposed to do - touch the stopper at full throttle and line up with the "V" mark at minimum throttle.