Do you get air in your bag? I had a hose between the thru hull and pump with a pin hole in it from the factory. An interior screw had just barely punctured it. It was well above the waterline so it wasn't sinking the boat or anything, but when the pump was filling it sucked air through that pin hole and totally screwed up filling. When draining it sprayed water all inside of the engine compartment (how I found the pin hole) and the bilge pump would kick on.