Teri,
There is actually a way to adjust the steering tension on the Motorguide models. (I found this out while dismantling mine last summer)
You need to let the trolling motor full down, and remove the screws underneath the head of the motor (where the cable from the pedal goes into the head/shaft). Take the top cap off, and you'll see some wires running down the center of the shaft top. There is a tension screw somewhere underneath that wire mount, I believe right where the cables attach to the steering on the shaft. It should be straight up and down. It takes a while to adjust and figure out the right tension, and it's difficult while the boat is on the trailer because the tongue gets in the way of the trolling motor lower unit. The tension screw adjusts with the shaft itself, tightening or loosening the shaft attachment in the head, so if you loosen it too much, the shaft will wobble out the bottom of the head. It took me a while to adjust, but it's definitely possible.
Thad