Not having any shore power connection, and a small outboard engine for on demand charging has forced me to be electrically conservative on my boat since I can not just plug in and charge the batteries up whenever I want.  The result is that I have upgraded all the lighting to LED lighting, and installed a small but capable solar charging system. This has worked out rather well and I am able to sustain my electrical needs for even week long live aboard trips.  The only downside to this is when I need to run small power tools or plug in a 110v device or charger, I have to dig out an extension cord with a shore power adapter and run it. That can often take longer than the project I need the 110v power for.

I decided to install an inverter at the same time I was upgrading the electrical panel.  I determined that something in the 400-500w range would probably be enough for my needs, which would mostly be for things like running the dremel or a heat gun to heat shrink electrical connections. I knew I didn’t want the inverter installed visible in the cabin, and I didn’t have any appropriate place to install it even if I did. I had a spot inside a hanging locker that would work great and sit just a few feet below the panel, but that meant I was limited to inverters with remote panels, which means 600w and up.  After some research and feedback from other sailors I decided that I would go with the Xantrex ProWatt SW 600 True Sine Wave inverter. I originally looked at the Pro Mariner TruePower 600 Modified Sine Inverter, but found that the remote only has a 10 foot wire, and it is not easily user extendable (read on to see why that is important), and for the small price difference the Xantrex is also a True Sine Wave inverter instead of a modified sine wave.

Having never wired an inverter before, my original plan was to wire the inverter to a dedicated 50A breaker on the panel as outlined below…

Inverter Diagram v1

Inverter Diagram v1

But after lots of feedback I changed my plans and decided to install the inverter back closer to the batteries following this general diagram.

Inverter Diagram v2
Inverter Diagram v2

My only concern with this design is that I cannot disconnect the inverter from the batteries without disconnecting everything else, and thus leaving some phantom loads all the time. So I decided to add a switch on the positive cable to the inverter.  I also decided to add a fuse to the main output since I had overlooked adding one when doing the initial electrical distribution upgrade. The final installation came  out like this.


Upgraded Electricial Distribution

Upgraded Electrical Distribution

I shortened the main battery cable from the battery switch when I wired it to the new ANL fuse block, which I put a 100A fuse in, then go straight down to the main positive buss bar, and over to the switch for the inverter. All wiring that feeds the inverter is 4AWG. I installed the inverter on a vertical bulkhead about 3 feet from the switch.  The inverter is only able to output ~6A @ 110v, so I ran 14AWG 3 strand cable attached to a weather resistant plug and plugged into the inverter…

Inverter - Mounted

Inverter - Mounted Inverter Close Up

With the other end wired into a plastic duplex outlet box, with a 15A weather resistant duplex outlet, and finished off with a varnished teak duplex cover.

Varnished Teak Duplex 110v Outlet

Varnished Teak Duplex 110v Outlet

The mounting location of the switch, while easy to reach and use, makes it difficult to see the LED indicating that it is powered on.  The remote switch for the inverter has a 12v input that is used as an “ignition interlock” so that the inverter cannot be powered on without 12v power being sent to that wire first. The intention is that you cannot turn it on unless the engine is running, and therefore preventing your battery from running low.  I attached the “interlock” wire to the output of the 12v outlets breaker so that the inverter cannot be turned on without having the 12v outlet breaker turned on, so that if the breakers are all off, the inverter is also off.

Inverter Remote Switch

Inverter Remote Switch

Since installing the inverter in the first week I have used to to run a power drill with a wire wheel to clean and prepare the surface for a new zinc, cut out the mounting hole with a Dremel Trio for the new stereo, and charged the battery for my cordless drill.

5 Responses to “Inverter Installation”

  • Gary Jones says:

    Trying to steal another idea or two. I have the standard Hunter shore power / battery charger setup and thinking about adding an inverter. I have three A/C outlets already wired into the shore power circuit. What’s the best way to wire both systems together so they can work off either A/C source? I rarely use shore power as I have a 20W solar cell running through a Gensun controller which keeps my batteries fully charged. Would it be better to run the A/C circuit off the inverter and re-wire the shore power to the batter charger only in case I might need to use that at some point.

    Your prop suggestion has worked wonders. Kudos for that one.


    • Gary, Most people I’ve heard of that want to do that use a combination inverter / shore power unit that combines those two functions into one and handles that source problem automatically. You could do purchase an AC transfer switch and install it so the outlets are powered by either the inverter or the shore power, but it’s important (and I believe mandated by ABYC code) that it be impossible to have both sources feeding the outlets at the same time as that can easily start a fire (aka using breakers that you turn one off and one on to switch the input source doesn’t comply).

      An alternative would be if you are only plugging into shore power once in a while, I would suggest considering wiring the outlets to run only off the inverter (or even better, run 2 of them off the inverter the other only off shore power, in case you want to plug in yet still run high load items like power tools). That means you can always plugin and run the inverter off shore power for longer duration light to mid duty loads (and not drain the battery), yet still run those outlets off the dock if you just need to charge a laptop or something, and then if you needed to run something heavy duty you can plug that into the direct shore powered outlet.

      The new hybrid inverters and shore power units are definitely the most versatile and easier option, but they may cost more than you are willing to spend for what amounts to a luxury item that will probably receive little use (speaking from my experience, my inverter was only used 2 or 3 times last year, and then only for short periods, however it was certainly very nice to have for those brief moments).

      BTW, I just upgraded the engine for this year, to better take advantage of the power of that new prop in rougher water (something you probably don’t see much of out there) Last summer I picked up a 2002 model year Tohatsu 9.8 short shaft, pull start, tiller controlled without charging system (the last year they made them essentially identical to the ones we already had), that I swapped a bunch of parts out with the old 8hp to convert it into a 9.8hp long shaft remote controlled electric start with charging system, and just finished last night rebuilding the 8hp into a short shaft pull start tiller operated engine. I should be going in the water in the next 2 weeks and will be posting an article about it later this summer after I have had some time using the new engine.


  • Gary Jones says:

    Brian, thanks for the info and warning. I have to pull my boat in the winter and it goes into storage lot until at least April 1st. Unfortunately my spot is 150 ft. from the nearest electrical outlet and I hate stringing that much extension cord. For a small A/C project I took an extra UPS, plugged in my sander and it worked like a champ. It’s a 1000W UPS, a little heavy and bulky, but it worked. Meanwhile, back to the thinking mode.

    Good job on the engine swap, I’m not that mechanically inclined. Maybe you have opened up a second career.

    • Gary, I’ve used my inverter many times for little things like a dremel or running a drill, and it does a great job for that type of stuff, but even with dual batteries wired together it can pretty quickly pull them down so on the rare occasion I need to do large projects requiring AC I run the extension cords too.

      As for the engine, it wasn’t that difficult, mostly was just a process to unbolt parts, swap certain parts between engines, and then rebolt everything together. I replaced a few older and worn parts in the process and some new gaskets here and there as necessary, but really these little engines aren’t very complicated, there isn’t all that much to them. Though to be fair, it does make it a little easier for me being that was my summer job growing up for many years helping my Dad at his shop rebuilding small outboard engines.


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