Mounting Batteries and other components...
 

I am trying to plan my battery / charging system that I will be adding to my boat and had few questions.

First off, I have an 08 210 SAN. The stock state is that it has a battery "hole" cut into the floor on each side of the boat, under the seats. The batteries run through a standard Perko switch.

I currently have already purchased two new batteries, Group 29 size flooded type (from Sam's). These will be replaceing the port side Interstate battery to be used for the accessories. They will be in parallel. Batteries are same age, unused, etc. I'm trying to decide how to mount them. So here are my questions.

1.) Should I enlarge the existing "hole" to be large enough to fit both batteries. The thought of cutting my boat, while practical, scares me. The batteries would be in the hole , but not in battery boxes.

-or-

2.) Should I mount both batteries (in battery boxes) under the passenger seat under the glove box, as far forward as possible. Why do people use battery boxes? Is it to meet a Coast Gurad regulation or are the unneccessary? They take up a lot of space.

3.) Next, I will be using an onboard charger. If I have the batteries charging with the seats down (closed) will I have a venting problem? Do I need to plan for additional venting, or do most people plug it up and forget it?

4.) I am planning on using a Prosport 20 charger. Where do most people mount it? I am planning on mounting it on a custom amp board that I am making to mount on the portside standard amp mounting location under the passenger seat.

5.) And last, if I need to extend the wires on the charger to reach my starboard (starting) battery, is there any harm in that? The line is already fused, and I feel fine about attaching a leader to it. I just don't want to spend $30-$40 for the "official" ProMariner extender if I don't have to.

Thanks in advance,

Chad