We suggest 10AWG to run form batteries to Perko switch and to units. Our battery install kit comes with four 6 AWG battery cables to go to Perko.If you choose to run main power to a separate fuse box then you only need 14AWG as 16V system carries the load much better than 12v and will not drop voltage, especially since you are running each device on a separate circuit to the fuse box.
The fuse box eliminates the factory fuse holders that are impossible to get to if a problem occurs on the water. But system will accepted other wiring harness from other suppliers.