My son called today he is working on a mower for a woman. She hit something and sheared the key on the flywheel. He replaced the coil, and fired the mower up ( blade fair and no harm to crank). It will run about five minutes then shut down. It won't restart until it has set and cooled down. Then restarts and runs for about five minutes and shuts down again. He has replaced the fuel line, cleaned the gas tank and carb and rest the coil gap to no avail. I am thinking maybe the coil is overheating and shutting down? Any ideas?