I have a Mag 7 about 2.5 years old that I use for my top off from the basement. It no longer will pump by itself. I have to take the propeller housing off, it then starts, as it is running I put the housing back on and it pumps but will not start up again. I have ordered a housing and a propeller. wondering whch is the main culprit that is bad ? As usual thanks in advance.