I have a Tsunami I/O and placed the batteries in the in deck bait/fish box that is in between the fuel tank and the front of the I/O box.
I have both batteries and the switch mounted in it with a hinged watertight hatch cover over it.
Works good for me,easy to get to and not a drop of water gets in it.
I only have a crummy picture of it when it was unfinished but here it is.
The finished pic shows the cover in the closed position (in front of the 2 rod holders)
