which bilge pump do i need with a manual / auto switch

[Bt Doctur]

500 gph, that barely enough for a shower sump.The pump is designed to keep you afloat in case of an emergency. Usually wired directly to the battery and should have an audible alarm wire to it.(motorcycle horn,etc)
Go small and go down.

 

[poconojoe]

You could, but don't go nuts with it. Just enough to activate the pump.

Very good point.
You don't want to submerge things like your starter, etc...

 

[wooky30014]

Knocking a little bit of dust on this one My "new" boat came with a pump on a switch so I went a step farther by adding a float switch and replacing the switch on the helm with an auto-manual with circuit breaker. The manual side only works while you hold it down and the auto is lit with an LED to show it's "armed". The bilge pump and the engine tilt are the only things wired directly to the battery, everything else goes through a battery cut-off