210 h.p. mercury m2 v6 wont rev past 3000

Got involved with a repo of a Sea Doo Challenger. Parts missing, bottom carb shaft frozen. Not running. Got it running, but wont run above 3000 and sounds like it is cutting out (rev limiter?)in the water. On the trailer she will turn 5200 with no apparent cut out.Scratchin my head. Tested resistance of stator and trigger assem. All right on track. Switch boxes tested about 200 ohms low, so not sure if this is the problem.Tested neutral switch. Shows open when in gear and has .004 ohms in neutral. Have read other places about a "Guardian" that can cause problems, but the manual neglects to say anything about it. Have 130+ lbs of comp. on all cylinders and the carbs have been cleaned. Guy who had the boat told repo company the same thing as I know, "Wouldn't rev over 3000" so he stopped making payments.Any ideas? It is a 2000 Challenger 1800.