Since I bought the boat there was a inline fuse and a spot for a spare connected to the battery. There was never a fuse in it. The pump works from the switch at the dash but while I was filling the bilge with water to clean it I noticed the pump didn't go on by itself. Could this be for the pump float? And if it is what size fuse goes there?

Although Velocity generally didn't connect the float switch directly to the battery - this is a tried and true approach. While the fuse size depends on the pump size, I'd suggest trying a 10 amp and moving up as needed.