I have a 24volt Ultrex 80lb I-piolet trolling motor, pulling a 20ft aluminum boat. My Ultrex seems to be always on number 3 or 4 as to power settings sometimes for hours at a time some times just for short periods. I can and do fish 10hr days occasionally.

My question is do I have to have two 12volt 100 amp hour batteries or could get one 24 volt battery maybe 125 amps?

The amp draw on the ultrex is 3amps per hr set on number 3 speed and 4 amps per hr set on number 4 speed.
What am I missing, the math says I can easily get 10 hours out of a signal 100 amp battery?

Its a cost issue for me so thats why I`m asking.

Thanks for any advise!