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Posted by on Apr 4, 2011 in Boat Maintenance, Safety and Seamanship, UK, US | 1 comment

Marine Wire Markings Deciphered

What's all that writing on a boat's wires? Ed Sherman explains.

Question: I’ve often wondered what all the cryptic printing on the wire and cables running through my boat mean. Is this something important?


No markings on boat wiring? That's the time to be concerned.

Answer: The short answer here is yes, it is extremely important. I’ve told people many times and I’ll repeat it here: it’s when you don’t see all the cryptic markings on the wire and cable that you need to be concerned, because it means it’s not marine grade wire.

The ABYC has some specific requirements for this marking within its E-11 electrical standard, and each needs a little bit of explaining.

First, the type and style of wire or cable needs to be identified. So, for example when looking at the photo here, you can see the tail end of some numbered reference and a UL reference. You can also see the reference to 14/3. The ABYC has requirements for oil and fuel resistance on the insulation jacket of all cables used on boats, so the referenced UL standard is in part designating that. The 14/3 is meeting another requirement which is to identify the size of the cable; in this case you are looking at a 3 conductor 14 AWG cable. The requirement also carries over to the individual wires making up the 3 conductor set in this example. With this information, a trained technician can determine if the cable or wire is sized appropriately for the amount of electrical current that the wire is expected to carry.

The rated voltage for the cable is also a required marking. In this case we are looking at a three wire (triplex) cable that has a voltage rating of 600 volts. This means it is quite adequate for handling shore power voltages. In contrast, DC wiring onboard is only required to be rated for 50 Volts.

Finally, the wire insulation temperature rating is also a required marking, in this case 105 degrees centigrade or 221 degrees F. This is an important rating because things can get pretty hot onboard, especially in engine room areas.

—Ed Sherman

1 Comment

  1. Great to see this explanation of boat wire labeling. The other thing I notice about this photo is the white outer jacket of the boat cable at the top of the photo. This is the typical color used in 120V US wiring, and likely contains black, green, and white conductors. A boat cable with the same labeling but a blue jacket is typical of 240V wiring, and would contain black, green and red conductors.