This Rule-Mate "Fully Automated" bilge pump features a solid state water sensing switch that eliminates the need for a separate float switch.
When water enters the bilge and reaches depth of 2-3/4", a sensor turns the pump on. After the water is pumped out, another sensor shuts the pump off at a water depth of 3/4". Unlike some other automatic bilge pumps, there is no on/off "test" cycling, and therefore no power use until the pump comes on.
The sensors measure dielectric constant, and will only recognize water. In the event of an onboard oil spill, pure motor oil that enters the bilge will not turn the pump on.
This pump has a 3/4" discharge outlet.

All-in-one pump and switch - no float switch required
Pump turns on when water level rises and shuts off when water is removed
Snap-off strainer for easy cleaning
Straight and 90 hose barb included
Non-fouling impeller
Completely submersible
Rust and corrosion protected
Silent, vibrationless operation
Moisture tight seals
Anti-airlock protection
Compact, energy efficient, long life motor
Able to run dry without motor burn-out
Marine grade sealed wiring
Stainless steel shaft
Ignition protected
CE and ISO 8849 certification
3-year limited warranty


Heavy on the technical side...

Note The capacity of ALL centrifugal bilge pumps, regardless of manufacturer, is rated at "open flow" - with no hoses or resistance to impede output. In actual use, however, the work of lifting the bilge water out of the boat will decrease the output of the pump. The higher the lift, the less the output.
For a smaller bilge pump like this one, expect an output decrease of about 8% per foot of lift about 85% of rated capacity when the outlet thru-hull is 2 ft above the pump, and about 75% of rated output at 3 ft above the pump. Purchase a higher capacity pump if that seems prudent.