Hello. I have a 1978 CHB. I’m installing a radio and new chart plotter on the flybridge. There is a “junction box” on the rear bulkhead under the dashboard which seems to join the wires from starboard side of the boat to the wires on the port side. At least that’s what it looks like. There is also a buss bar with only ground wires. I’m looking for current to determine how to do this but can’t find a live circuit anywhere. All 12v systems work but this wiring doesn’t seem to be energized at all. Is anyone familiar with this? Thanks for your input.