Trolling motor wiring help

[Dramad1]

I took my kayak (nucanoe unlimited)out to.el cap today, its been a few months since taking it out. Day was slow but managed 3 dinks by the end of the day.
Day was going fine, hit all the usual places, decided I was going to explore the far back as I never travel that far nor have I seen many people go back back to the back. Turned the bend and started heading back, cranked the trolling motor up to full power (motorguide xi3).
10-15mins of travel i was about half way back. I started smelling a burning smell, I looked back and seen the negative side on my pig tail to the 12v 100amph battery smoking. I quickly cut the power and Inspected the wiring. Negative side plastic sheathing was melting, wire was hot. The positive side was normal and cool.
The motorguide xi3 connects to a marinco plug in the front of kayak, 6g marine grade wire runs through the boat to another marinco plug in the rear. About 12' of wire. The marinco plug in the rear is connected via pig tail (16")with 6g wire to a newport vessels battery box with built in fuse. The fuse is inline with the positive wire(red), it did not pop.
After I cut the power to the motor, I drifted for 15-20 mins. I inspected the terminals and wires at that time and let everything cool down. I pulled up the trolling motor and rudder and began to paddle. 10-15mins in, I maybe move 50-80', it was a losing battle with the wind and current and such a heavy kayak.
I decided I needed help and chanced the trolling motor, battery looked fine and was cool to.touch, power cable now cooled, I started the motor on its lowest speed setting and began paddling. Constantly checking the wiring on the pig tail. All seemed fine. Decided I wasn't moving fast enough and increase speed a bit more and continued to paddle and monitor pig tail, motor and wiring.
This continued for 30 more minutes, eventually getting the motor up to half speed. At this point I just wanted to get off the water before I got stuck out there trying to paddle my butt in from the far back. It was a mission but I managed my way back to the launch.
Loaded up and inspected wires, just the negative side on the pig tail. Motor fine, battery fine, fuse still intact, marinco terminals look normal. Headed home and decided on the way that I may need to rewire my kayak with maybe 4g wire?
Could running the trolling motor at full speed for 15mins straight cause excessive draw on the battery? I've never had issues before, I've been to most lakes around San Diego county front to back full speed, put a pretty hard load on the motor and battery. Never ran the battery empty yet, motor has never had any issues other than dead battery in the remote and try to maintain motor after each trip, clean, remove prop, remove any build up, oil the release bars etc.
Im still pretty new to being off the bank in my kayak, never had a boat let alone a trolling motor. This kayak and motor/battery has had about 80 trips out. I feel the trolling motor itself is not enough to power the kayak and or not intended to pull the kayak around like a actual motor. I have been thinking of adding a nk300 to the rear for traveling and use the trolling motor as a.trolling motor spot lock once at fishing location. Still undecided as the added weight, additional battery etc.
Long post, my apologies. I guess I'm looking for help, suggestions, thoughts and what could have caused this, recommendations. Should I rewire the kayak. Do I need a different battery, is this normal when under heavy load.
I'd really appreciate any help, ideas though, thanks everyone in advance.