Hey hawk invest in a deep cycle battery and put it a 15AMP CHARGER WHEN COME in from fishing get automatic charger with a maintaner on a good marine battery will last a long time I have 2 marine batteries in my boat that over 10 yrs.old Hammer.
Yes it looks like you have a bad battery are you using your cranking battery to run your trolling motor? you need a battery for your trolling motor by it self Hammer.
I work on trolling motors ever day go with a 24v it pulls less amps than a 12v motor and batteries will last longer I would go with a 80#motor a 17 ft. is pretty heavy with a 80#motor you will have plenty of power. Hammer.