okay, after replacing the thermostat, risers, water cirlulator, the manifolds cleaned and inspected, new plugs, oil change, i think i only have one thing left, the impeller. and that was changed at the begining of the season (although i did hit some muck a while back.) ran the motor at the slip for an hour after doing all this work with no overheat problem, stayed about 150 degrees. got it up to just below 180 at 3500 rpms for a couple of minutes, backed it down to idle and temp went back down. took it out for a cruise and them was good till i throttled up to cruise, took about 4 minutes at 3500 rpms and it reached about 200 degrees, throttled back to idle and temp went down almost immediatly back to about 170. is the impeller not keeping up with the engine rpm while in gear? i'm lost. if thats my problem, that would be great. the good news is it dosen't backfire anymore and runs great with platinum plugs! HELP!!!!! 