I have a Mercruiser 470 that runs fine but when the engine reaches temp it usually will stall when throttled back to neutral. Wont restart until it cools, usually about 30 minutes. Mechanic said spark is fine and sprayed just a touch of starter fluid into the flame arrestor and it started and ran fine. It had an electric choke which we though was closing but found it was not. We are stumped. Any help is appreciated.