Rather than getting the water out, they should be preventing the water from coming in. With a dry boat, you can go for years with a flaky bilge pump and not know it. All I have is a manual bilge pump, and that was installed upside down (suction on top) from day 1. Pump idle, the flappers would hang open. Finally after 35 years or so, the flappers stiffened and wouldn't close in cold weather - no prime, no pump. Now have new pump with suction on bottom - all is good.