I would like to move my battery (s) to the front of the boat and install a blue sea systems isolator and battery switch... My question is what gauge wire would you who have done it recommend to run power from the battery at the front to the starter of the motor in the back. Thanks


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I've used a SO cord with #4 and it did well but if I did it again I would use #2 just for over kill.


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There is a chart somewhere or formula or something....can't remember what it was...but, you factored into it the length of cable, the amps needed and it tells you what your minimum wire size should be.

Having said that, I only did this for my trolling motor up front, batteries in the back. Judging by the size of wire going from my battery to starter....I'd say some pretty heavy stuff! LOL


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#2 should be plenty...

http://www.engineeringtoolbox.com/amps- ... d_730.html

A quality 4 gauge OFC should suffice. A quality 2 gauge cca should also. Whatever you do, buy quality wire. Check out knukonceptz or sky high for good wire at reasonable prices. OFC is usually tinned which will tolerate the marine environment a little better. It's more expensive, but can also handle more current than the cheap cca stuff so you can get by with a little smaller wire. I'd probably run 1/0, but I'm a fan of overkill on electrical.

Thanks guys for all the info!!


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I have a 20' lead of #4 and have run it this way in the last two boats over the last 8 years with no problems. Gatortrax will make you a dual #4 battery cable with lugs at the length you specify.

That's the one I used, SpecialK.


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#4 of any good wire should be plenty I would think. depending on how big the boat is (length of run) and how much that starter actually draws will tell you exactly what you need but just as a comparison its not abnormal to use #4 wire in a vehicle to support a 100a draw. Because of the short duration of draw from starting you shouldn't have any heat issues with the wire but may get a little more juice to the motor from a nearly dead battery using larger diameter wire. Also if the boat will see any salt at all I would recommend tined OFC but if you do use CCA it will probably last 3-4 years before giving you any problems. another benefit to using wire like Knukonceptz or kicker wire is that their 4 gauge will actually be slightly larger than the standard size along with a higher strand count and will pass more current.

if you do decide to use cca as it is much cheaper or even welding wire which will be OFC usually without a tined coating be sure to seal the ends of the wire with liquid electrical tape or something similar and then shrink wrap them as well to prevent water intrusion which will ruin the wire.

Problem with jumper cables is that its not tinned wire. They will last some time but not long like marine wire.

^^^^ this. I originally used CCA jumpers from battery to motor. Within 2 years the cable on the motor side deteriorated to dust from saltwater. Changed out cables to 4 ga tinned wire from tinnedmarine. All the other wiring in my boat is either duplex or triplex tinned wire from them also.

And just fyi, you guys can get tinned cca wire too. The main thing is buy from a reputable company so at least you know you're getting what you're trying to order. Lots of shady shit on the wire market.

Its not cheap, but I like to buy mine from west marine. That way I can put my hands on it ahead of time.