Picked up a used MK 80# 24V Ultrex. Wiring in the boat is to small (8 awg) at 20 ft. so I will need to upgrade. TM manual says I'm good with 6 awg at 20ft (56 amps) but MK website says 4 awg at 20ft. Question: Is 6 awg and 4 awg that big of a difference? What would you do? I just want to do it right the first time and not worry later on if I did the right thing. Thanks!

If I were going to pull new wire. I would pull 4 awg. It will handle a larger TM if you change it out in the future.

99% of the boats out there have 6 ga wire (or smaller). It will work. 4 ga would theoretically be better. Doubt anything you would notice.

If you go with 4 ga, could be a problem with connectors and maybe tools. All my tools are for 6 ga or less.

Amazon has the 4 ga x 20' at $89. 6 ga x 20' at $64.

The leads coming off the peddle is 10 awg if that make any difference.

That is fine if you connect it to the battery/s directly. Adding more wire to reach the battery/s is where the increase in wire size is needed. Wire length adds resistance, increase in diameter lessens the resistance.

Got'cha! Going with 4 awg.

6g is plenty. Don’t waste money on 4g. If there is a chance of getting a bigger troller, it will be a 36v. 36v draw even less amps that the 24v. Concentrate you money and efforts on making the best, most reliable connections on the ends where the wire gauge changes and at the battery(ies). And buy tinned marine grade only.

Just received 4g duplex marine wire from Amazon, thats some big chit!! I could return it and get the 6g or just go with what I have. This will be my last TM (boat) just ask my wife.

4 gauge is over kill. But……ya got it now. It should last the life of the boat.

Everything I do is overkill.

Tools and connectors. Make sure 4 ga connectors will work. Hard enough to step down to 10 ga from 6 ga. You probably will need a buss bar of some sort. Easy to make.

Heck, in the old days, we ran the TM off 10 ga all the way. Not a good idea, but we know more now than we did in 1975. Silvertrol 24 volt. 15' Fisher Marine.

You're gonna need one of these to crimp connectors correctly. Worked great when I did mine.
Crimper