2003 Carver Mariner 350. When the vacuum pump runs, it starts out quiet then bangs like someone knocking on the door. Anyone had similar? What did you do?
Pumping the liquid (with weight to it) and when it hits air it starts to jump around. The mounting brackets are loose or broken on the pump itself or maybe the rubber isolators are worn out on the feet where they mount
This or it's possible that your vent is clogged and the water it's pumping cannot be pumped into the tank.
I ve had two doing this... One had a loose motor assembly, all 4 bolts to the plastic brackets where gone and the motor and gear where flapping around. The other one is a mystery, all the bolts are tights, rubber mounts too. Only knocks 4 or 5 time as vacuum peaks before turning off. One of these ain't broken enough to fix it
one other thing if the hose is relatively new And If the distance from the pump to the toilet long check and see if the hose is secure to some thing at least every 2 feet