I believe you have the jabsco pumps. If the shut off valves are open and the motors are running and no water is being pumped into the bags then your impellers are most likely shot. The impellers are pretty robust, even the old original ones. I still have 2 original 9 year old impellers and one green one that I replaced the in 2009 when I got the boat as It was not working. To winterize I pull the bags then stick a hose in a container of rv antifreeze and hit the drain button for about 4-5 seconds or a litre/quart then pull the hose out let the pump drain for another 5 seconds. This is my 10th season with original impellers. Fwiw