Two - A primary and a backup slightly higher in the bilge. Both have float switches and are indenpendently switched, fused and connected to separate batteries so thay are completely redundant systems. The primary is on a bilge pump counter which displays how many times the pump has cycled on. That way it can't mask a small problem until it becomes a big one. The backup pump has an audible alarm.
Also have two hand pumps....and a couple buckets.
Also have two hand pumps....and a couple buckets.