My personal opinion, if your planning on trolling with a small motor, bite the bullet, and get yourself a small gas powered engine. 4-6hp.
Forget the electric motor for trolling in the big O. My top of the line terrova with ipilot etc was ok on FLAT lake. As soon as the currents kicked in, or the waves were bigger than half a meter, it was useless.
Also, if your main motor fails, forget of getting to the shore on the electric crap. Small gas powered one will get you there