You can use two group 27 batteries wired in parallel. It will pull the boat
around all day long. By putting them in parallel, it doubles the run time.
The AC Delcos are 160 minute reserve capacity batteries. By putting them in
parallel, it gives me 320 minutes of 25amp capacity.
You need to get deep cell batteries with the highest amp available. Check
amp draw on different model motors and get one with a low amp draw at full
power.

What is Amp Draw?

.. Amp draw is the measurement of electrical current drawn from a storage
battery (or battery), while the trolling motor is being operated at maximum
speed.
.. Minn Kota 's published amp draw figures represent actual on the water
conditions (with all of the motor 's wiring, switches and circuitry in the
electrical system as the test measurement is taken).
.. Approximate length of running time when operation a trolling motor at full
power can be determined with a motor 's amp draw and the battery amp hour
rating.
Example: A single 120 amp hour, 12 volt battery and a 12 volt trolling motor
drawing 20 amps at the highest speed setting will run for about 3.4 hours.
.. The formula for the calculation is as follows:
..85 A.H.R. = Hours of running time. (A.H.R.= Battery Amp Hour Rating)
M.A.D. (M.A.D. = Motor Amp Draw)

.. As the speed setting is reduced the motor amp draw is also reduced.
.. A motor drawing 30 amps at high speed may only draw 5 amps at the slowest
speed. The same motor that will theoretically run about 3.4 hours at high
speed will run for over 20 hours at the slowest speed.

Sarge