Does your trolling motor have a selector switch. I am not familiar with the particular model you have. I know on my Motor Guide has a 3 way switch on the foot pedal. In the center everything works like normal. Switch it to the left and it will run all the time at whatever speed you have the dial set on. You do not have to push the button. Switch it to the right and no matter what the speed dial is on as soon as you depress the button your on 100% speed.
If your's has the same switch as mine you may have it set so to run full speed no matter where the speed dial is at. If that's not it then I have no idea.