I felt I had to move the battery switch given the previous construction. Three large gauge battery cables were thread thru a small bulkhead opening without chafe protection, wired directly to the batteries without fuse protection. Seemed like an electrical fire waiting to happen.Just use all tinned wire/connectors and components and you shouldn't need to treat the connections with anything. Just keep them clean and dry.
So when we bought our boat the DC panel was a mess. The AC panel was unsafe romex number 14 wire and a Square D residential Load Center.
Survey did not even mention one word. So the first project was to pull out all the wiring and install new. one 250 ft roll of #12 wire and 250ft roll #12 duplex and 100ft roll of #12 three strand ( ac )later all of the interior wiring was replaced. At the same time I built a new Panel with Blue Sea components. Project was well worth freezing my butt off during the winter.
I retired my 1987 38-200 last winter and replaced the panel with a blue sea unit mounted in a "door" as others have mentioned. I found a lot of wire that was bare copper ( no tin). Badly corroded. I still have the old panel which seems ok functionally. I would be happy to send if receiver pays shipping.