I didn't want to put a separate dedicated bilge pump in each hull, and it is of no real use to have full-time electric bilge pumps in a catamaran anyway. I just wanted a single, general purpose emergency pump for when we are underway.

I put the pump in then center of the boat so that it could be used by just laying an intake pipe down into either hull from the center bridgedeck and the output pumped out into the cockpit. I put the pump under the floorboard just inside the companionway door. I bolted the pump to the board from the backside. This is what the top of the floorboard looks like.

I used a swimming pool pump discharge hose so that it would be really small when stowed and used an "official" bilge pump intake hose for the input side. The procedure is that you just turn the floorboard upside down and stand on it and lay the intake hose (white) wherever the water is, and put the output hose (blue) out into the cockpit or even over the gunwale (it is 12ft long). Standing on the board will keep it stable while being pumped. Everything stows neatly under the floor.