you can't go too big on the electric trolling motor..so go as big as you can afford
don't get a solar charger, they don't work
I don't see any reason to get a cover for the battery, but I guess it wouldn't hurt
I would go with a battery charger with a minimum of 5 amp charge, a 10 amp smart charger is even better..
if you only had a 3 amp charger and your battery was way down say 100 amp hours, it would take at lest 33 hours to charge it
5 amp 20 hours
10 amp 10 hours...and ...call me crazy but some times I want to go fishing to days in a row