I have a 1978 Evinrude 85 hp V4. I just bought the engine and it starts fine but after running for about 5-10 minutes the engine will not stop after turning the ignition off. I need to choke the engine to get it to stop. I have only run the engine a few times due to other repairs that I had to make (replace Water Pump assembly and themostat assembly) I was told when buying the boat (1975 Starcraft American 15') that this problem existed.