I had the same setup on my jetboat, before I re-wired it. Had the buss bar mounted on the transom, one for the + wires, and one for the - wires. Although it was covered by an engine cowling, it was right near the corner of the cowling, and it wasn't really a waterproof design, so, my buss bars were partially exposed to the elements.
This kind of buss bar is what I used:
To connect all the sets of terminals, you could use a strip, or, you can make short jumper wires.
I sealed both of the buss bars with liquid electrical tape, using the red color for + and the black for -
Never had any problems with mine. Just be sure to use closed-ring terminals, not the open 'forked' type, to ensure a good solid connection.