My fresh water tank is full and the water pump does not work. I can see water up in the hose about 5 inches below the pump, but the pump will not draw water up! I assume I need to replace the pump or a gasket. The problem is, there is not enough room between the top of the pump and the companionway step to pull the pump out. Is it OK to unscrew the sink and drop it, in order to make room to pull the pump? Has anyone done this and is it difficult? Thanks for help.