Which Color Cable is Starter?

My boat was broken into and my stereo system was stolen. When taking the amps they disconnected the two batteries and Perko switch. Now I'm trying to hook the batteries back up and am a little confused. It appears I have 4 wires that come up by the battery. One is a very large red cable and a large black cable. Then I have a thinner red cable which i assume is all of my lights, blower, etc. and a thinner black cable which I assume is the ground wire for lights, blower, etc. I have been told to hook the starter cable to the common terminal on the perko switch but don't know which cable they are referring to. Is it the larger red cable, small red cable or thinner black cable?

I am thinking that the large red cable should hook to the common terminal on Perko switch, the large black cable should hook to the - terminal on battery #1, the small red cable should hook to + terminal on battery #2 and small black cable to - terminal on battery #2. And then hook a wire from + terminal Batt #1 to terminal 1 on Perko and hook a wire from + terminal Batt 2 to terminal 2 on Perko. Then my amps should be wired from Batt 2 directly to amps. Is this right?

Your pretty close bro. Sorry to hear about the vandals in your boat.

Large Red cable from floor is the Alternator to Perko switch.
Generally its the Center of the switch.

Large Black cable is the Primary ground and this goes right to Battery 1

Now there's 2 Medium Red cables. 1 to each Positive terminal of your batteries comes right out of the Perko switch.

Smaller Red and similar size black cables, this is the power and ground to the Fuse block of your boat. These both go to Battery 1 positive and negative respectively.

There should be a medium sized Black cable just lying around this is Negative from Battery 1 to Battery 2