Asking for a friend, he has an older 50 hp Mercury outboard. I'm not sure of the year and model. Engine starts and runs. Runs fine until you shut it off. Once it's shut off and after it has ran for a while and is warm, it will not take gas and dies out. It will start right back up and idle, but will not go forward until it cools back down. Once it cools back down the engine runs fine again. Any ideas?