DC Wires and Cable 101

DC Wires and Cable 101

I was originally going to have this article be based on what type of wiring and cabling you SHOULD and SHOULD NOT use aboard your boat, but the list would be long, boring, and overwhelming. After having my second cup of coffee though, I decided this article would be most beneficial if I just went over some terminology and what type of wiring and cabling you SHOULD buy for your boat’s DC (Direct Current… From a Battery source) electrical system.

The terminology you will see below is what we use in the marine world. When it comes to almost anything electrical, there are a plethora of different meanings to the same word. A residential electrician, a marine electrician, and a nerd building a time machine in his parent’s basement will all have a different definition of what a wire is. So, with that said, these definitions will not steer you wrong when it comes to your boat. Outside of that though, you are on your own.

Wire:  18awg to 8awg is considered wire.

Cable: 6awg to 4/0awg is considered cable.

Conductor: Any material that can permit the flow of an electric charge through it. The conductivity (how easily the electric charge flows) of materials varies greatly and is measurable.

Insulator: Any material which restricts or denies the flow of an electric charge through it.

AWG:  an acronym for American Wire Gauge. This standard, which was created in Rhode Island in 1856, defines the width/thickness of the wire. Also referred to as “gauge”.   

Positive Conductor:   Is a current carrying conductor. Typically referred to as the “hot wire” or “positive wire”. Also known as the “ungrounded conductor”. For DC applications, this conductor’s insulation should be red.

Negative Conductor:  Is also a current carrying conductor. It is a negative return conductor. Typically referred to as the “ground wire” or “negative wire”. Also known as the “grounded conductor”. For DC applications, this conductor’s insulation should be black or yellow.

To start, the wire or cable should be Marine Grade. I know you are probably thinking the term “Marine Grade” on products is just a way for the manufacturer to bump the price up 150% on a generic product. For some products, you would be correct. When it comes to wires and cables though, there truly is a difference. A Marine Grade wire/cable is manufactured to endure one of Mother Nature’s harshest environments… the marine environment. So, let’s break down the beautiful manufacturing benefits of a Marine Grade wire/cable.

Marine Grade wire/cable conductor material is tinned copper. Copper is a great conductor of electricity. Tin is not. The reason for the copper being tinned is for corrosion protection. Tin offers a very measurable level of corrosion protection compared to if the copper wire remained untinned or “bare”. It should be noted, that ABYC Standards due allow the use of untinned wire/cable aboard your boat. As far as my standards go… I will ONLY use tinned wire/cable aboard a boat. Many tests have been performed over the years regarding tinned vs untinned wire in the marine environment. Tinned wire/cable outlasted untinned wire/cable every single time when it came to corrosion.

Marine Grade wire/cable also has finer strands of tinned copper than non-marine wire/cable. Not only finer but many more strands as well. A Marine Grade wire can be anywhere from 10% to 20% larger than that of an SAE Automotive wire. There are a couple of awesome reasons for this. One, marine-grade wire/cable is better equipped to deal with the vibration and flexing of the boat hull while underway. And two, less voltage drop. The more copper in the wire/cable, the more conducting material there is to be able to carry the electrical current to your device/load.

Marine Grade wire/cable insulator material is quite different than that of non-marine grade wire/cable. A Marine Grade wire/cable insulator material aka the insulation is manufactured at a minimum to better resist moisture, oil, and heat. The insulation material slightly varies from manufacturer to manufacturer. Most use a PVC-type material. And I say “type” as most manufacturers simply list their insulation material as a “Proprietary Blend”.

Another key element to the insulation of Marine Grade wire/cable is the various numbers, acronyms, and words marked on it. View the below photo of the breakdown of each marking.

As you can see from the above photo, there is more to look for than just the term “Marine Grade”. At a minimum, the wire or cable should meet these standards:

  1. Have an Underwriters Laboratories (UL) listing of UL1426
  2. Insulation shall be marked with the following: type/style, voltage, wire size, and the dry temperature rating.
  3. If wire or cable is installed in an engine space, the insulation shall be oil resistant and have a dry temperature rating of at least 75°C.
  4. Wire and cable shall be stranded copper. The strands shall be categorized as either type 2 or type 3.
  5. Wire and cable shall have a minimum rating of the nominal system voltage.
  6. Wire shall be at least 16awg. (18awg is acceptable for “pigtails” less than 7 inches. “Pigtails” are the wires which come installed on a device or piece of equipment from the manufacturer. For example An anchor light assembly.)

Here are the most prevalent ABYC Standards regarding wiring and cabling aboard your boat:

E- Minimum surface marking of the individual conductors and their jackets shall include:

E- type/style

E- voltage

E- wire size

E- temperature rating, dry.

E- Conductors shall be at least 16 AWG.


 1. 18 AWG conductors may be used if included with other conductors in a sheath and do not extend more than 30 in (762   mm) outside the sheath.

2. 18 AWG conductors may be used as internal wiring on panelboards.

3. Conductors that are totally inside an equipment enclosure.

4. Conductors on circuits of less than 60 V having a current flow of less than three amps   in communication systems, electronic navigation equipment, and electronic circuits.

5. Pigtails less than seven inches (178 mm).

E- In engine spaces the conductor insulation shall be oil resistant and have a temperature rating of at least 167°F (75°C) dry.

E- Conductors and flexible cords shall have a minimum rating of the nominal system voltage.

E- The construction of insulated cables and conductors shall conform with the requirements of:

E- UL 1426, Cables for Boats

E- Conductors and flexible cords shall be stranded copper

Now to dive into the American Wire Gauge (AWG) system. This system of measurement is funky. Well, not funky, but counterintuitive to what your brain wants to initially think. The higher the number, the smaller diameter of the wire is. So, an 18AWG wire is far smaller than an 8AWG wire. Then, when you get down to the number 0, it gets even more fun. A 0AWG cable is typically written as 1/0AWG and pronounced as “1 Aught”. A 00AWG cable is written as 2/0AWG and pronounced as “2 Aught”. And so forth until 4/0AWG. With 4/0AWG being the largest diameter cable under the American Wire Gauge system. And now you are probably wondering what the heck “aught” means. From what I can gather, the term “aught” means “nothing” or “zero”. There seems to be a lot of history and debate on this. So, if you have some free time, and no longer wish to read my sweet articles, Google the term “aught”.

Last, but not least, and what most of you are hoping I touched based on…. What wire/cable manufacturer should you go with. Well, when it comes to the various manufacturers of Marine Grade wire and cable, just make sure they meet the minimum standards addressed above and you will be good. There are many reputable manufacturers out there these days. I mainly use PACER Group and ANCOR wire and cable. Not because I deem them to be the holy grail, but because these manufacturers are readily available to me. Another manufacturer I see available but have yet to use is Cobra Wire and Cable.

Well, I hope this article has provided enough information and guidance when it comes to purchasing the proper wire and cable for your boat. If you are still unsure or unconfident on this subject, please do not hesitate to reach out. Having the proper wire and cable on your boat is crucial to a successful and safe electrical system.

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