For the past week I was trying to solve this problem. 97 gp1200.. compression,exhaust, spark, waterhoses, carbs, reeds, prop and pump all good. But I was only getting 5000 rpm and 35 mph. Than I check the ignition cables,plug cap, and coil today according to the manual using a voltmeter.
The first spark plug cap was not sending any current thru. So I replaced it. The ignition cable and coil was fine. Even with defect cap, the plug gave good spark. Haven't gotten change to test, but could that be an sufficient reason for turning 5000 rpm and low speed?
Anyone had this problem before.

R11