Well im certainly no authority but ill tell you what i have and
how its set up. Fist off i have a Minnkota Riptide 55# thrust.
Its bow mounted on a 17' Key West center console along with a 90
hp main engine on the transom. Its primary use is keeping the boat positioned while drifting. Also slow trolling for crappies
etc. Its rigged up 12 volts with its own battery. Both batteries
are linked by a selector switch allowing the use of either or
both. I have an onboard 2 bank charger which is always plugged in to my house current when the boat is not in use maintaining both batteries. The Wall Mart marine batteries are now 3 years old. While my use may differ from what your describing ive not had a power failure during a days use. If it will be a primary power source id be seeking other advise as to how its hooked up. As for the size id say the 55 would probably be acceptable.
