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A very common problem for boat owners is not having sufficient gauge (size) of wire to carry the required current to the device. Not only are you drawing more amps then specified by the device, but the device that is connected is not getting the proper voltage level it needs.

Below is a table that indicates the maximum distance your can run wire based on the gauge of the wire and the maximum amount of current the device will draw


Note that there are a lot of good calculators out on the web.

For example, I had a windlass originally installed on my boat that drew a maximum of 40 amps at 12 VDC. The wire run was about 25 feet with 4ga wire. It met the criteria for wire gauge but just barely.

I replaced the windlass with one that draws a maximum of 80 amps at 12 VDC. The table indicates that I need to replace the 4ga wire with 2ga wire which I painfully re-pulled. Note that I had some wiggle room since the table indicates that 2ga wire at 80 amps is good out to 30 feet.

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