I have an 89 50hp force. It started overheating on me. I replaced the impeller and thermostat. No luck. Took it to the dealer. They replaced water pump housing. Told me it was fixed. Took it out and it overheated at low idle. Ran fine wide open. Took it back to the dealer. They tore it down again. In their water tank it had no problems. Just to be sure, they took the head off and flushed everything and replaced head gasket. Sent me home. I took it out and it overheated at low idle. Any suggestions are greatly appreciated.