Welcome aboard. There are countless ways to do what you propose. I would get a 12v battery
that has screw on posts for the pos anneg sides of the battery. Then buy an adapter like you get for a car trailer
that is flat and has four plugs. wire one side to the bilge pump
and the other to the battery when you want to pump
on all you need to do is plug
the pump into the connector when you want it off then you can unplug it. as an alternative you can put a switch in the poistive wire. Installing a Bilge Pump by Don Casey
Here is a link to a more complicated automatic pump.
Between us there was, as I have already said somewhere, the bond of the sea. Besides holding our hearts together through long periods of separation, it had the effect of making us tolerant of each other's yarns -- and even convictions. Heart of Darkness