We gathered actual flow rates and power ratings on all the bilge pumps at two voltages while pumping water into a tank set five feet above the pump using saltwater.
Each pump was mounted to our test bench and connected to a fuse panel using the factory wire leads. The appropriate size fuse was used in each pump circuit.
ABYC standards, say a bilge pump should be able to dry run at design voltage, that’s 13.6 volts for a 12-volt pump, for at least seven hours without failure.
Naturally we added a test to confirm compliance with this standard. The dry run was accomplished in two steps, first, we warmed the pumps up with 2 hours of running at 12.5 volts then we jacked the voltage up to 13.6 for the next 7 hours. Total continuous dry running time for each pump was 9 hours. All of them passed.
Flow testing was done as a two-step process on one pump at a time, testing both at 12.2 volts and 13.6 volts. Voltages and current draw were both measured at the power supply. As each pump was run, it was timed and the pumped water quantity measured, allowing calculation of each pumps flow rate.
Here are the setup details. Two plastic tanks were used, one as a supply tank and the other as a receiver tank. The supply tank was a 200-gallon container supplied with saltwater from a dockside canal. Prior to each pump test about 60 gallons of water was put into the supply tank.
One at a time pumps were placed at the bottom of the supply tank and held in position. For discharge hose, we used appropriately sized nylon reinforced smooth bore PVC tubing recommended for use as bilge pump discharge hose.
All discharge hoses were 10 feet long. At the other end of the hose we installed a plastic bulkhead fitting, typical of one you’d find installed aboard most boats. This end of the hose was placed into the top of our receiver tank, a 22-gallon plastic tank marked in 2-gallon increments. The receiver tank was located five feet above the level of the pump.
Electricity was supplied to each pump from our power supply through 20 feet of #14 wire to the fuse panel and then on to the pump.
Wiring on each pump was looked at closely. First, we determined whether or not the wire was constructed of tinned copper, as is the consensus recommendation of marine electrical experts. We also checked the wire size, insulation temperature rating, insulation voltage rating, and of most concern to an installer the length of the leads.
In our opinion, bilge pump factory leads simply can’t be too long. It’s best to have as few connections as possible between the pump and the bus bar providing power. This lessens the chance that corrosion will attack the pump wiring. If the leads are too short you’ll be forced to add more wire with a butt. This gives corrosion another avenue into your wiring.
In the final analysis, we picked pumps for use based on performance, warranty, wiring, and price.