I have a jon boat also and I just got a deep cycle battery from Costco. I just got the Kirkland brand and the first one lasted over 6 years before it wouldn't hold a full charge. I just replaced it. The battery lasts a long weekend for me without requiring a recharge.

I use a Mincota on board charger that I picked up on clearance that does a good job. Before that I was dragging out a car battery charger to charge it and maintain it.