Trolling Motor Problems

I really need help from one of you "boat/mechanical" experts.

I've got a great 20' Bass Boat with Dual Pro Battery Charger and an Evinrude 58 lb thrust trolling motor that has hardly been used.

Anyway, the trolling motor is a 12/24 volt unit, and the power sucks. It used to be great, but ever since I took off the cables and put them back on, the power has been terrible.

I can't believe I've blown the motor by somehow crossing the wires/cables, but I just don't know.

Any ideas here? My batteries are brand new.

Do I need to "cross" the cables somehow? Is there an adjustment?

Can it have anything to do with the little square electrical gadgets on the ends of the battery cables? I've never known what those are.

Or do I just toss this motor in the trash and get a new one.

thx