My boat came in two versions, one the inboard diesel, and the other the outboard.   For some reason the outboard version did not come with a main battery switch, so the electrical fuse panel and VHF are always powered, and everything just gets attached directly to the battery terminals.  Since before I bought the boat I’ve planned to install a battery switch, clean up the wiring and just upgrade the electrical in general. It took me quite a while to figure out how I wanted to do this, but this spring I finally decided what I wanted to do. This is part 1 of the electrical system upgrade. Part 2 will be replacing the 5 position fuse panel with a custom made breaker panel from Bass Electric later this summer.

Below is the decided upon design. I purchased 100 amp bus bars for the main power distribution as I think my max non-starting draw with everything on and the VHF transmitting is around 25 amps, but as I don’t know exactly how many amps the engine draws when starting I decided to stay on the safe side and attach the engine cables to the same terminal posts on the bus bar as the power feed cables so the engine starter cables would be directly attached to the  battery feed without drawing through the bus bar.

Click for larger version

 EDIT: see the post about the inverter installation for additions to this system

The two batteries sit in battery boxes in the stern on the starboard side, and the engine controls and start / charge wires from the engine reside under the port side hatch. I decided I wanted to mount everything on the bulkhead above the batteries, but due to the thickness of the bulkhead, I could not screw into it without the screws sticking out into the cockpit, so I needed to mount a piece of plywood to attach everything on. Also the shape of the bulkhead requires 2 separate pieces.   I found a remnant of nice 3/4″ hardwood plywood at Home Depot for $1 that is perfect for the job.

Since the battery switch will put frequent torsional loads on the screws when turning on and off, and is something that may be removed and re-installed a few times over the life of the boat, I didn’t want to use a wood screw that may eventually work loose or strip the hole out so I decided on 1/4″ machine screws threaded into Tee Nuts on the back of the board, and since the board needs to sit flush, I countersunk the Tee Nuts into the back of the board.


Close up of the countersunk Tee Nutimage
Prior to installation I sealed the front and edges of the board with West Systems epoxy using the 207 clear hardener  to help prevent moisture from getting into the wood and rotting it. When I was ready to install the board I covered the back of the Tee Nuts with a small piece of tape so the epoxy did not get into the threads.
Here is everything laid out before heading to the boat for installation.
Since the whole reason for using the plywood is that I was attaching to a thin bulkhead that I didn’t want to drill holes in and have the screws coming out in the cockpit, I needed to epoxy the boards in place.  Since epoxy takes a while to cure, I really did not want to sit there and hold the board in place for an hour or more. I used the 205 hardener, but the air temp was around 45 degrees so the set and cure time would still be rather slow. I picked up some $4 spring loaded compression type curtain rods from target that would fit between the plywood and the hull to hold it in place while I left the epoxy to cure overnight.

I cleaned the surface and washed with acetone, then test fit the boards and compression poles, adjusting the lengths to keep a nice firm pressure and hold everything in place.  Once I everything had been test fit, I mixed up the batch of epoxy and set it aside for a few minutes so it would begin to setup, and applied a strip of masking tape along the bottom edge of each piece of wood to prevent epoxy drips, then brushed a thick coat of epoxy on and stuck the boards in place with the compression poles holding them in place overnight.

The next day I returned to the boat and installed everything on the new boards.  The small terminal block at the top connects the wires from the solar panel to the input side of the solar charge controller.  Having the two separate boards also serves to create a “always hot” area that can potentially always have voltage, and a switched area that never has voltage, if the battery switch is in the off position.
I also cut off the old connectors and re-crimped new connectors on all connections, then sealed them with adhesive lined heat shrink tubing.  Some of the old connections were starting to look pretty old, and most had not been heat shrunk so it was time to replace the old connectors anyway.

To give you a better idea of where this bulkhead is, that is the rudder post sticking up behind the negative bus bar. It is about 16 inches to port from the plywood panels.

EDIT, Here is a old picture of the cockpit pre bimini (actually from before I even owned the boat), I circled the bulkhead that the panel is installed inside of, in red.

11 Responses to “Battery Switch and Electrical Distribution Upgrade”

  • Ron20324 says:

    I think i would have raised the buss bars up enough that you could clamp at least the battery cables to the board. I just redid my ground system and buss bars very much like you so i could add that VIC600 also.

    • You can’t see in the picture, but the cables to/from the house panel bairly reach the buss bars where they sit. If I moved the buss bars up even a couple inches I don’t think they would reach. I may move them up later if I replace the main wires feeding the house panel.

  • I can’t see how the buss bars were raised. But thanks for this tutorial. I’ve finished in less than 2 hours of upgrading my battery switch.

  • Chad says:

    Hey Brian, I have a 1992 Hunter 27 outboard & tiller version like you and really like this electrical setup you installed. Question–if you have your batteries turned “off” are you still able to charge them with the solar panel?

    Thanks and enjoying your blog!

    • Chad, Yes the solar panel will still charge the main battery with the switch in the off position, but not the secondary. I have considered adding a ACR to allow it to charge the second battery but so far haven’t felt it worth the cost or minor power draw for an otherwise simple setup.

      I’d love to see pictures of your boat to compare differences!

  • Kurt Hannig says:

    Brian need to do something with my batteries and wondered if your batteries are in the starboard locker? I can’t reach mine and have to get the wife to install and remove. The battery boxes are loose on the bottom of the locker as you can’t reach them to install screws.
    So thinking
    A: move them to under the seat at the head of the table by the v-berth where the hot water tank was, (tank removed was leaking) and mount the tank back where the batteries were.
    B: install a access through the rear bulkhead to access the batteries
    You have any ideas or how do you gain access on yours?

    • Kurt,

      My batteries are in fact in the starboard side of the lazarette. for any practical purposes I cannot reach them from on deck either, but I can fit down through the locker (legs first, stand up, arms straight up, squat down, once “sitting”, bring arms down Reverse procedure to get out.) without too much discomfort or contorting. You might want to try that before you consider relocating them.

      As for the relocating itself, these boats tend to sail better (especially in chop) with a little extra weight forward, so somewhere in the V-Berth area would be good from that perspective, but you need to consider the routing of the battery cables, and it would probably require heavier gauge wire to accommodate the extra length of the run. One upside to this would be if you mounted the battery switch right there under the table in that wood panel, which would be easy to access (Assuming you don’t have the inboard engine panel with it mounted on the panel I have seen some of our boats have).

      My transducers are located just forward of that space, and require access through there to clean the paddle wheel, so I couldn’t locate the batteries there myself without interfering with that.

      Installing an access hatch in the bulkhead can be done, I’ve read someone did exactly that to fit a new holding tank in the boat, but that requires a bit of work to do properly since that bulkhead is structural, so you need to be careful not to weaken it too much, or it may start to crack. I would only install a commercial hatch with a solid frame to fit inside the cutout, unless you are able to fabricate one yourself.

      All in all, the easiest option is just to climb down into the lazarette and install the necessary screws, but relocating the batteries forward does have some advantages to it in ease of access to check water levels and possible battery switch placement. As for putting the hot water heater in the lazarette, you’re still going to have to find a way to fit down there just the same as the batteries, as well as re-plumb the water lines, so I don’t see any benefit to that.

      • Kurt Hannig says:

        Well I’m still not sure what I’ll do. Even with moving the batteries I would like a hatch. More usable storage would be nice. As you know this boats have everything but storage. The rear bunk is turning into a collector of stuff and I’m getting tired of moving it all to open and close sea cocks.

      • Storage is always the biggest challenge on any boat, these especially! Check out the aft storage compartments I added a year or so back, it helps a lot, and was cheap and simple.

        I am considering building a shelf system in the lazarette on both sides (aka above the batteries), check back in the spring to see how that idea progresses.

      • For what its worth, I use the V-Berth as storage, and sleep in the art berth…

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