Still, these figures give a good indication of a pump’s capability. For boats up to 18 ft, a 500 GPH pump will do. Up to 22 ft, you may want to consider a 700 GPH model. All boats over 26 ft will need something over 1,000 GPH at the very least. The more gallons a pump can shift, the better, but for the best results, it’s always wise to have two pumps on the go, rather than just relying on one. [links]