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How to wire this AC panel ?

Sep 14, 2009
Macgregor 25 Mo
I got this AC panel when I bought my Mac 25 swing keel a year ago. I have a Marinco 30 amp 125 volt shore power plug on board, but I'm not sure how this panel wires up to that plug or how I go from the panel to a GFI. The shore power plug has three # 12 wires coming out of it. Red and two Blacks. I cant see any model numbers anywhere. I am planning on using 12/3 marine grade stranded wire for the panel to GFI.


Jun 6, 2006
Hunter 40.5 Harrington Harbor North, MD
Clearly the PO did not care about getting the wire colors correct. Should be black (hot don't touch when energized), white (neutral, grounded after the panel breaker) and Green/bare copper (safety ground at the ground buss). Thinking you actual want 12-2 as that has the three wire 120 volt circuit you are looking for. 12-3 is for 240 volt and has 4 wires. The ground wire is never counted in this naming convention.
With all that said you have a 2 breaker setup. The hot and neutral each get their own breakers. Those would be the ones at the "top" of your panel. two breakers operated by one switch. The ground is NEVER run through a breaker and is not on this panel. Probably a buss bar on the hull behind where the panel installs. The neutral will also have a buss or will share the ground (not the DC ground please but I've seen that done too)
The short black wire going from the topmost breaker to the copper buss has me concerned as that is not a very smart way to set things up unless there is a secondary AC panel somewhere. The big screw hole is just begging to some niophyle to connect the hot here. That would be where the hot from a second panel should be connected.
The hot from the shore must only be connected to the topmost breaker on the other terminal from the black wire. So power comes in from the shore hot hits the breaker, goes through the breaker and goes to the black wire and that feeds the copper bus which feeds the hot side of the rest of the breakers (except for the breaker just below the main hot which is where you connect the neutral to. ) The switched side of the neutral should connect to the neutral buss which is somewhere else on the boat.
So now all you have to do is determine which colors on you shore power cable connect to which terminals on you shore power female plug. A multi-meter and the shore power cable (run it back to the panel install location and multi-meter to test for continuity). The various male plugs and what each terminal is connected to used to be available at WM help pages. I'm sure it is on the web somewhere so google it.
The shore power ground should connect DIRECTLY to the ground buss with no breaker.

Good luck
Jun 6, 2006
Hunter 40.5 Harrington Harbor North, MD
the second breaker has a "GFI protected" sticker on it. What ever it connected to, AC outlets I hope, will have the GFI outlet that all the other AC outlets are daisy chained off of.
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Maine Sail

Feb 6, 1998
Canadian Sailcraft 36T Casco Bay, ME
Some considerations when installing a 120V single phase marine AC system. This is far from covering it all but is a start.

Any AC panel on a boat should have a reverse polatiry indicator circuit. That panel does not have one. If it does not have a reverse polarity indicator then each branch circuit needs to be a double pole breaker just like the main AC breaker. Without a reverse polarity circuit each branch breaker needs to interrupt both the AC HOT/BLACK and AC NEUTRAL/WHITE. Your panel can't fit two more double pole breakers so a reverse polarity circuit would be required. This could be achieved by installing a double pole breaker, preferably an ELCI, with reverse polarity, ahead of the panel you have. it is preferably installed as close to the shore power inlet as is practical. If the wire distance, not the as the crow flies distance, between the shore power inlet and main panel is more than 10 total wire feet this breaker needs to be there anyway.

#2 AC NEUTRAL/WHITE and AC GROUNDING/GREEN must remain isolated on-board the vessel and can only be bonded back at the shore power supply. The only time AC NEUTRAL/WHITE and AC GROUNDING /GREEN can be bonded on the boat would be when a genset or inverter are operating as the AC SOURCE. Once these sources are shut off, that the NEUTRAL/GROUNDING bond needs to be broken.

#3 AC GROUNDING / GREEN needs to be bonded to the vessels DC ship ground bus but NOT AC NEUTRAL/WHITE.

#4 Current safety standards require an ELCI main breaker. That panel does not have an ELCI.

#5 If plugging into shore power you will want to install a fail safe type galvanic isolator.

#6 Beore wiring any AC sytems on boats please study, and fully comprehend, the current ABYC standards as there are differnces/nuances betwenen shore and boats that are critically important.

#7 Also take some time to research Electric Shock Drowning.

#8 If you don't understand the AC system nuances mentioned above please consider hiring a professional who can wire your boat to meet the current safety standards.. AC and boats can kill.

The diagram below is the easist way to properly install a 120V AC system on a boat. However, it assumes you have a reverse polarity circuit which would need to happen with your AC panel before you could use this diagram. You could do this by installing an ELCI with reverse polarity before the AC panel. In other words your panel does not work as a marine AC panel if following ABYC standards.. For safety reasons, any installed AC system should follow the ABYC standards.

Jan 31, 2009
Macgregor & Endeavour 26S and 37 Utah's Canyon Country
As you can see from Maine Sail's post doing it right is going to cost money and a fair amount of work and doing it right is the only way to do it for your safety and others. I just don't see a real need for AC on our trailer boats. If fact I removed it on the Endeavour and see no need for us to have it there.

At home I'll run AC on a cord attached to a GFI outlet on the side of the house and do the same on the Endeavour in the yard while working or living on them. On the water it is all 12 volt appliances for us and we don't miss AC on the water at all.

If you are going to have the boat, regardless of size, in a slip all or most of the year then I could see doing it. Not sure how you plan on using your boat?

1300 miles to The Bahamas and Back in the Mac...
Endeavour 37 Mods...

MacGregor 26-S Mods...http://purplesagetradingpost.com/sumner/endeavour-main/endeavour-index.html
Mac Trips to Utah, Idaho, Wyoming, Canada, Florida, Bahamas
Sep 14, 2009
Macgregor 25 Mo
Yes , I'm getting ready to put it in a slip. I was thinking of a Paneltronics model 72313. What do you guys think ?
Jun 6, 2006
Hunter 40.5 Harrington Harbor North, MD
MS is of course correct. Been rewiring my new house and forgot about the neutral and ground (on boats) only get connected of the soruce of power is also on the boat. If you are getting shore power at the dock that connection is made on the shore side at the meter box on shore. Which brings up the need for a source selector switch. Not a problem for Shine as he did not indicate an inverter or genset
Aug 22, 2011
MacGregor Venture V224 Cheeseland
Yes , I'm getting ready to put it in a slip. I was thinking of a Paneltronics model 72313. What do you guys think ?
I put one of those in this last summer - I'm pretty satisfied with it so far.

The branch breaker switches are really easy (too easy?) to flip to OFF
but I don't see there being a problem with that since the panel is out of the way.