I need some ideas. My '82 sail drive will not idle or run at low RPM's. It runs great at high RPM's but as soon as I slow down it dies. Will start in neutral but dies immediately. Will start in gear (forward or reverse) but throttle has to be engaged about one third speed. According to the mechanic everything that can be adjusted has been adjusted. He seems stumped. The motor has recently been apart to replace the impeller. Has anyone experienced this problem and know the fix?