A lot of this is going to depend on how much electrical equipment and electronics you're putting in the boat. Also, you should probably say whether you are planning on adding a shorepower circuit and panel to the boat or not. Many smaller boats don't have a shorepower inlet or panel.
A good basic setup that includes an AC shorepower panel, and two battery banks would require:
A Shorepower inlet 30A like this one from Sailnet's store
A Shorepower AC panel with dual breakers for the feed, single breakers for the other circuits. A good one is this one from SailorSolutions, and gives you three AC circuits for your boat.
A shorepower based battery charger—size it based on your battery bank size. Iota makes a very good unit, that is reasonably priced.
At least one GFCI outlet for every AC circuit you have aboard.
Two battery banks, the house bank should be larger than the starting bank if you're planning on taking any longer cruises.
A main battery switch like the Dual Circuit Plus from Blue Sea, which I like because in normal use it isolates your house bank from your starting bank, and protects your electronics from the starting voltage drop/surge that can occur. It allows you to combine the banks in an emergency.
Fuses for the positive battery leads, like the Megafuse from BlueSea—again sized for the loads you'll be putting on it.
A battery combiner or echo charger to charge the starting battery bank whenever the house bank is being charged
A DC distribution panel:
If you're planning on ganging multiple items on a single breaker, I suggest you run a single wire from the breaker panel to a fuse block or fused switch panel like this one and power each piece off of the panel, so you can size the fuses for the individual pieces of equipment.
Also, highly recommend you try and minimize the different types of fuses you have aboard. I've gotten my boat down to basically three types—ATO blade fuses, MaxiFuse blade fuses, and MegaFuses for the main battery leads.
You should use adhesive lined heat shrink crimp connectors, like the ones found here
. The crimping tool looks like this:
And you should use good tinned marine-grade wire, like Berkshire cable, which you can get here
A good primer on crimping marine electrical connections by our friend Maine Sail is here.
I'd highly recommend you use YELLOW for the DC ground wire insulation color. If you use black, it can be easily mistaken for an 120 VAC hot lead and vice versa... which could be really bad for you. At a minimum, you should have five colors of wiring on your boat.
—hot 12 VDC
—12 VDC ground
Black—hot 120 VAC
—neutral 120 VAC
—Ground 120 VAC
Click on the photos to see where you can get the item pictured.
I hope that helps a bit.
I purchased a '77 Catalina 27' over the weekend and my first priority is to fix the wiring. There are 3 brand new switch panels in the galley, but very little wiring for anything and what is hooked up is done so for temporary use (no fuses, wired directly to the battery, etc.). Can someone please post pictures of their wiring set ups and diagrams that can give me some ideas how to get started and what parts I will need to consider purchasing?