dual battery buziness

[Mr.O]

yes, everybody says its really easy, but they forget to mention it can be a pain in the ***. for me, i've got a 96 supersport. first i have to move the battery to make room for fat sacs which means i'll have to make longer cables. no big deal, but then i run into the other wires on the battery. one set i will guess is for the bilge, but the other wire on the positive terminal screws me up. its got a fuse and needs to be hooked up to the battery for the boat to run. (i can't do the test for your alternator where you take the positive off to see if the motor will run).
so how do i wire this to the other battery?

[SquamInboards]

RE: dual battery buziness

it's all relative, the SS is easier than a lot of boats because you have lots of room for the batteries, they're not wedged in behind or under some seat or small under floor compartment. You should run the existing wires to the switch and put the switch somewhere so you don't have to extend the existing cables, then run a positive wire to each battery and one between the grounds on the two new batteries. At least that's the easiest way, in my opinion. It can be nice, though, to be able to reach the switch without having to lift the power hatch - in our SS it's easily reachable if you pull up the backseat, in case the battery dies with the hatch closed.

[Mr.O]

OK, that sounds easier than i had imagined. so just to clarify the bit on existing wires - which are the ones on the battery that feed relays for ignition and fuel injection. these just simply go to the switch with the positive?

a question about the switch.... i picked up a perco from west marine that's rated 250 amps continuous, and 300 amps intermittent. i would imagine this will do?