Rewiring a Mac25

[Gregory Ulrich]

This is my first post on this forum though I've been actively reading through it for a couple months now. We recently purchased caguy's MacGregor 25 and have been enjoying it immensely. It's our first boat so we're pretty psyched.

One problem we have found is with the electrical system. Because all of the connections are located in the bilge, oxidation has caused an almost complete loss in continuity (solved by removing fuses and licking them before replacing them LOL)

I'm planning on relocating the panel, 12v battery cut off, terminating posts etc. to the bulkhead nearest to the entrance and replacing fittings and the old wire with Ancor 12 gauge duplex. It's a simple 12v system and aside from some minor wire rerouting, I'm not planning on changing anything,
Maybe I'll add a through hull connector for a solar panel.

The battery is charged by 12v charger connected directly to the battery and I would like to utilize the outboard engines 12v power and have an option for solar. My question is do I need some kind of a diode to prevent power from feeding back into any of the charging systems(shore power, solar, outboard)?

 

[Dan Johnson]

Gregory...

I would use an A/B battery switch to isolate one form of charging from the other.

You're on the right track with Ancor duplex wiring!

 

[Barnacle Bill]

You have to use stranded wire to comply with code. 12 gauge is pretty heavy for lights and most items (like light bulbs) on a MacGr 25. You can get away with a smaller gauge which will save you some money. Polarity is not important for most 12 volt lights, but it is for motors. Shore power is another matter. Polarity is very important there and larger gauge wire is important.
If you have two batteries you should have a switch that reads 1 or two or both or off. If you have a battery charger it should be hard wired in to the system through a proper shore power inlet (30 Amp 250 volts for your size vessel). This will have 3 wires (black, white and green) which is consistent with the shore power cord (30A), the dock power and it should be run into an AC switch panel which has double pole breakers. I suggest that you have one breaker switch for the shore power itself, another for the battery charger. Blue Sea products have these switches and breakers, for one.
The AC shore power panel is separate from the 12v system.
Code requires double pole breakers for the shore power, but only a fuse or breaker on one side (hot side/red) for the 12v system.
If you have two batteries then get a charger that will charge two batteries and wire it accordingly. Usually 10 gauge wire is suitable from the charger to the batteries, but the instructions with the charger probably will tell you what to use. Use Ancor solderless terminals sized right for the wire used for connections.
If you have any AC outlets in your boat, the main breaker switch can be used for those, but you must have a GFCI outlet near the head or galley sink and if the others are down the tree of outlets, then they will suffice there too and keep your insurance company happy.
It is not recommended that you run an extension cord into the boat to power a battery charger, but millions do it.
That's my 2 cents.