I bought a used perko switch and not sure about how to wire it in. What I am wanting is factory battery to start the boat and run everything like when the boat came from the factory. However I am installing a amp with subs along with two Optimas and only want the subs and amp to run off of the two OPTIMAS not the other battery. However I want ALL three batteries to be getting charged while the boat is running and want to listen to the subs while running down the lake. Any help on this would really be appreciated.