According to
their website, it looks like a group 24 battery has 70-85 amp hour capacity and the 50 lb thrust trolling motor has a draw of 50 amps, so you'd get about 1.7 hours out of the battery at full speed (85 ah/50a=1.7hrs).
That's just based on minn kota's numbers and will depend on your boat size, wind, current etc. I have a 100ah battery and an Endura Max 55 lb on my 14 ft canoe. According to Minn Kota, the draw of the trolling motor is 50 amps, but the max uses less battery than the standard Minn Kota at lower speeds. After a day of fishing (usually 8-10 hours) I typically have more than 75% battery left and thats after driving ~15-20 min to the spot at full speed, usually some light trolling, and moving while casting, and then driving the same distance back at full speed. Someone with a more similar sized boat may be able to provide a better estimate for your situation but I hope that helps!
