Trolling motor problems!!!

So I am having issues with my trolling motor. It's a minn kota 55 lb thrust transom mount trolling motor. All the electrical works fine but the issue comes in when I twist the throttle... It goes from nothing to full speed as soon as I turn the handle in both forward and reverse... I have looked online and haven't found anything about this problem, so I am just wondering if someone has had this issue before or any tips on how to fix it?? I emailed minn kota today. It really drains the battery when you have to use full power all the time. Thanks for any info and help!

It is a 2004 minn kota maxxum 55t. I emailed their tech service and they just said that my speed control switch is bad, but on this model i dont think there is a switch... All i could find online was just the control board.

The mother board took a crap. Very common problem.

Model? Does it have discrete speed settings, or "infinite"?