I recommend the following total-bilge-pump capacities as rules of thumb. Boats less than 20 feet: 1,000 gph; 20 to 25 feet: 2,500 gph; 25 to 32 feet: 4,000 gph; 32 to 36 feet: 6,000 gph; 37 to 45 feet: 8,500 gph.

What size boat requires a bilge pump?

WA – A power or manual operated bilge pump capable of pumping 4 kilolitres per hour is required for all boats 7 metres and over.

Do I need 2 bilge pumps?

It is always better to put in a second thru-hull.

Check valves can clog up, preventing both bilge pumps from pumping water out. There's also the fact that any hose of a given diameter can only handle so much water. You will be lowering the pumping capacity of both pumps since they will be fighting each other.