I use a 24-volt 80# Terrova on my 20'er.
I don't think you have to go over a 12V 55# either.

I would get a GOOD battery though. I run 4 of the DieHard Marine Battery Size 31m in my boat, and they are Great..

Of course you would only need one. The weight may be a concern though @ 75# each.

For my 80# thrust, I very often run 10 hours straight, at about 1/2 to 3/4 throttle and don't even come close to running them low..

As said before, Get a good charger...

Old Fishermen never die, we just get reel tired.

May you build a ladder to the stars
and climb on every rung.
May you stay......Forever young