Are those AGM batteries? Something isn't right. I have an Interstate regular deep cycle battery in my dump trailer and plugged in the onboard trickle charger for 24 hours and was surprised even though it showed a full charge, it was only 47% on my portable charger. I pulled the battery and charged it on a real charger. How long was it on the Minn Kota charger?
Mine are standard wet cell batteries. I always plug in the boat right when I get home and leave it overnight. This is using Minn Kotas 3 bank Precision Digital MK330PC charger, I have been told it's a good one but maybe it's got an issue.
I have a Schummacher charger that when connected tells me what the battery charge is. I also have that same Minn Kota charger ... I believe I read somewhere it takes more than overnight to fully charge a discharged 100 ah battery. I don't believe your batteries were fully charged.
Here you go Jethro...hard core agm batteries with better amp hours than the noise Mac is pushing...designed to run electric outboards...https://www.elcomotoryachts.com/product-category/accessories/batteries/I may actually upgrade! 36v with over 600 amp hours is wickedly impressive.
Well, my batteries are indeed torched, they fail load testing and they are out of warranty. Awesome.
That sucks sorry to read. However much better than the motor being spent.