pcator, assuming the pump setup is similar to some of my old boats, it may be safer (after pumping the water tank dry) to loosen the waterpump connections - at least the one with the lowest tubing, to drain out the water from the impeller area. Usually not too hard to do. Or, you could splice a "T" valve into the pump intalk with an open tube to just suck a tad of 'pink stuff' into the pump impeller.
John