Wiring

A boat electrical system is never “feature complete”. You will always find something to add or modify, and wiring that’s exposed to the elements will eventually corrode. We were lucky in that our boat came with a well thought out and documented 12v system for critical loads. However, we’ve added a second house battery system (described in detail in the “Energy System” doc), and reworked maybe 1/4th of the original wiring. Wiring was one of the simpler things to learn on the boat, but it’s also easy to quickly waste money buying the wrong components and equipment. Below is what we’d do if starting over.

Crimping, Connectors, and Terminals

Most of marine wiring work is crimping ring terminals, spade terminals, and butt connectors to a wire range of 22 - 8 AWG (wire thickness). When installing new systems you will deal with 6 AWG and below (larger wire), but for the vast majority of our wiring we use this crimper from Ancor. It is a “single crimp” tool designed to work with marine heat shrink terminals, instead of the automotive nylon terminals and “double crimp” crimpers. These terminals are more expensive, but completely protected from moisture and much easier to work with using this crimper. We initially did most of wiring with nylon terminals and cheap crimpers, and eventually replaced everything with this combination.

For specifically which terminals to buy, we mostly use Ancor. They are even more expensive, but we have found a difference in our usage. For less critical work, it can be nice to have cheap wire terminals as well. As far as sizes, we mostly use the “blue” (14 AWG - 16 AWG) ring terminals, with a “size 8” ring. We do still need other ring sizes, and also use the “red” (18 AWG - 22 AWG) ring terminals pretty frequently. The “yellow” (10 AWG - 12 AWG) sizes aren’t often used as we step up to copper wire lugs (this for example) and larger wire crimpers. Concerning spade terminals, we use them occasionally (“Scanstrut” plugs assume them for instance), but often prefer ring terminals because they can stack on top of each other on a stud. According to the ABYC standards, you can stack up to 4 high before needing to move to another stud.

For other connecting and crimping tools, we sometimes use Ferrules. These are a metal cylinders that go around the bare wires, and makes it easier to slide into “spring clamp” connectors (and only the “spring clamp” kind — not screw down kind). These are often used on inverters or controllers. They are normally worth the extra hassle and tools. For solar connections, you will also need a dedicated crimper and hardware.

In order to connect or join wires, prefer WAGO Connectors over wire nuts. We use all the 2, 3, and 5 way splitters often, so it’s worth having an assortment and getting as wide a wire AWG (wire thickness) range as possible. These are great because they have a great hold, and it’s often that you will need to change your original wiring in a year or two. If wires need to be joined in a water proof way which won’t come undone, we use heat shrink butt connectors. WAGO also makes waterproof connectors, but they are even more expensive, and the Ancor butt connectors can accept different size wire and are more than secure enough.

The final kind of connector we use often, are Anderson Connectors. These are best for larger gauge wire (8 AWG and below), and things that will be plugged and unplugged frequently. Trolling motors often assume this kind of connection, and we’ve used them a lot when we are testing something out. For instance we ran our house loads for awhile from a battery that we charged via a DC to DC charger in our car. The battery had an Anderson connector attached to it, and it would plug into the DC to DC charger, trolling motor, and our home via Anderson connectors. Anderson connectors do corrode with enough time, but they are significantly better than trolling connectors, and are fast to replace.

Wiring Tools and Wire

The crimpers mention will be most of the tools that you will need, but there are a few more that come up. For all of these we have survived with the cheapest versions, so we are unable to say if upgrading makes a big difference. First you’ll need to find a way to strip wire of all sizes. We have one tool for 8 - 16 AWG, another fro 14 - 26 AWG, and yet another for 8 AWG and below. The 8 AWG and below tool is a pain to use, and is probably worth upgrading if you cut these wires frequently.

For shrink tubing, we often use what’s included with the terminals, or pull from a pack of different sizes. In order to apply heat to shrink the tubing or adhesive, we previously used a butane torch. We eventually upgraded to a heat gun, which is a recommended upgrade for a cleaner install.

For wire, we buy flat marine grade “duplex wire” like this in many different AWG sizes. Wire is expensive, and you often need much more than you think you will. Having said that, we mostly keep 10 AWG, 14 AWG, and 18 AWG on hand, and buy larger sizes only when it’s needed for a project. When we were testing out the house loads we also kept a lot of 6 AWG and 8 AWG on hand for instance. For cable glands you’ll often need “round” wire like this instead. It’s much thicker than you would expect, but flat wire won’t do well for closing gaps. For purchasing wire, we buy it all online because it’s much cheaper, and hardware stores don’t even carry what we need.

As a final note, be very careful cutting the sheathing of “duplex wire”. You often need to cut feet of it off the wire, and most people seem to do this with a knife. We did this with a knife as well, until eventually it slipped and led to a hospital visit. We now move very slowly with these. Please email a better solution if you know one.

Fuses, Fuse Holders, Switches, and Distribution Blocks

There are many different kinds of fuses out there, but we now use ATC, ANL, and AMP. We initially used “resettable” fuses for some applications like this, but they would always get stuck fused or open after awhile. In general, fuses are highly variable and not built well as you can see from this stress test. Still, they are what we have, and we try to put a fuse 7 inches away from every battery (or as close as possible) and oversize wire a bit. That’s probably not necessary, but it makes the list of things shorter to buy, and isn’t that much wasted copper.

Our main work horse fuses are ATC “blade” fuses. We like these more then glass fuses, and they are easy and cheap to swap out in a fuse block. If you only need one, the inline fuse options look like this and this. It depends on the application, but we normally prefer the kind where the wires are both coming down vertically rather than horizontally as they seem more compact. When you need space for many fuses, but don’t want negative bus bars included this is a good option. Otherwise when full circuits need to be supported, prefer this style. It’s normally worth it to pay extra for the “Blue Sea Systems” branded products. We’ve used the non brand name kinds, and while they work, everything feels a little “cheaper” with incorrect sizing. They are probably all sourced from the same company anywhere, so your milage may vary.

Concerning switches, if you aren’t using the distribution panel directly, automotive “Rocker Switches” work well. We prefer the kind without lights to tell you if they are own, because the lights used a surprisingly large amount of electricity, and are another thing to hook up. We also prefer the kind with “spade connectors”, as there is often little space to maneuver, and there is no benefit to ring terminals as they can’t be “stacked” in this case.