mercury trolling motor repair help?

[srimes]

Hey I picked up a couple of trolling motors off craigslist, both only run in reverse: a minn kota 48lb with the PWM "maximizer" and a little mercury "thruster plus" with set forward and reverse speeds. The minn kota only has 2 wires running to the motor and when I power those it runs forwards or reverse full speed as expected. If I can't fix the controller I figure I can use a scooter controller.

The mercury however has 4 wires running to the motor: a big red wire, a big yellow wire, a thiner yellow w/ red stripe, and a thinner yellow w/ black stripe. Can anyone tell me what kind of motor this is and how to power it?
Here's a pic of the mercury: