Perko switch question

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.

You want wire the engine battery to the #1 position on the Perko, and the amps batteries to the #2 on the perko. When the Perko is set to the number 1 position, that is what wil be powering everythig, so that is what you want when starting your boat, and that is what will be getting charged. Running in the all position, both battery banks will be powering everything, and is a good position for the Perko while running, as the alternator will be charging everything. When you set the Perko to the 2 position, your stereo batteries will be powering whatever is on, and is a good position for the Perko, as you will not be running down your starting battery, and will always be able to start the boat.
Depending what size alternator, what size stereo your powering, and how much your running vs. sitting, the alternator probably won't be able to keep all batteries at a full charge, so I suggest plugging your batteries into a charger at the end of the day, and keeping everything topped off. Batteries stored in a less then full state of charge, will shorten their life considerably.

A mechanic told me that I killed my batteries by running on the both switch because the batteries were 2 different groups. Not sure if this is true, but when I replaced them I got 2 identical batteries and never had another problem, granted I did sell the boat about 6 months after the new batts.

Thanks for the help. So I asume that the current red(positive) battery cable that is going to the original battery will be hookied to the center post on the Perko. I think that I will also put a inline switch between the two Opitimas and the amps so I can make sure that I can cut the power off to the amps 100% if I want to.

Thanks for the help. So I asume that the current red(positive) battery cable that is going to the original battery will be hookied to the center post on the Perko. I think that I will also put a inline switch between the two Opitimas and the amps so I can make sure that I can cut the power off to the amps 100% if I want to.
No, the positive wire from the battery will be hooked up to #1 on the perko, with the other battery bank hooked up to #2 on the Perko. The center post is the common post, and will power everything.

Or do a search (little button near the top), so people dont have to answering the same question over and over. Plus you'll find wiring diagrams that people have drawn up.

Thanks for the help with everything. I am going to wire it all up this weekend.