I'm using one of these for my 12v 55lb Minn Kota Endura Max (supposedly more efficient motor) and I push about 400lbs of stuff all day with it. It's a bit pricey being a deep cycle AGM, and heavy, but at 100ah it's a good match for MK's recommendation. I charge it overnight after each trip and the lowest it's been is 40% after a whole day of heavy use (fighting wind). The motor has a 'gas gauge' and so does the (cheap) MK battery box I have it in.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
ps- If you're looking for a smaller place to test the boat and fish Furnace is nearby.
