minn kota terrvoa 101

I have a 22 foot north river aluminum boat its roughly 3000 pounds. Im looking to buy a minn kota terrvoa trolling motor to attach to the bow of my boat but I have a few questions. First should I got with the salt water version of the trolling motor or the original black model. Second how many battires could I have hooked up to the trolling motor, just three being its a 36 volt unit. And last how long will the motor last on the water if im trolling at 2.5 mph. If anyone has one of these units on their boat please help me out.