OK FELLOW BOATERS .I HAVE A FORCE 50 IT HAS A NEW IMPELLER AND A NEW THERMOSTAT. AT SLOW SPEEDS IT RUNS GREAT BUT WHEN I INCREASE THE SPEED IT STARTS OVERHEATING WHEN I LOWER MY SPEED IT STARTS COOLING DOWN AND RUNS WITH NO PROBLEMS ANY IDEA WHY THIS WOULD BE HAPPENING. I'VE CLEANED EVERYTHING...