That's what happens when you either don't have a tank, the tank is totally waterlogged or someone put a valve between the pump and tank and closed it. By the way, your motor is a gonner if you let it keep doing that.
Did this "Pro" have an air compressor with him to blow out the tank and add the air pressure? It took him an hour to change a switch??? Did he do anything to the tank. Just so you know, changing the switch won't cure the problem.