Replacing a bilge pump

My bilge pump took a dump. The separate float switch was screwed up too so I'm replacing both. Each was wired separately to the separate switches on the dash. Purchased an Attwood pump this morning from Wally world that has the pump and float switch all in one. According to the wiring instructions, it's made to use with a single 3 way switch. Manual--off--Automatic. Can I wire this up to work with my existing separate dash switches? There are currently 2 wires going to the float switch and 2 wires going to the bilge pump. There are only 3 wires coming out of my new pump. I'm guessing that the single ground wire coming from the new pump will connect to both ground wires coming from the switches. and then each hot wire (one for the manual and the other for the auto) will connect to the hot wires from the switches. This should work right?

Also, the old pump and float switch were screwed into the hull. Is the hull thickened there (with glassed in plywood or something) to accomodate screws for pumps and such? I'm guessing that my mounting holes aren't going to line up and that I'm going to have to add some holes for this new pump.

On my 82, the bildge mount is a 1/2 inch piece of plywood covered with a couple of layers of glass. I'm not much good at wiring, but I would have guessed as you did - both grounds to one wire. BKH

I got it working. As I mentioned, I originally had a 4 wire set up. There were 2 black wires to the switch and then a black and brown to the pump. The new 3 wire I hooked up only had one black wire (ground). When hooked up and working properly, I had a black wire left over. My solution was to tape it up out of the way. Probably not the way some would've done it, but it works and the install looks neat.