I have a Yamaha on my Lund Fisherman…. the gauge on mine is just this little tab back by the mount on the motor. Mine came loose once, and another time broke. Cheep, easy fix. The little tab works against a button if I remember right. Takes a little screwing around to adjust right, but…..
Unless maybe your motor has a different setup, you can go back there, and by hand push it and see it works the gauge. When broke, mine spun and didn’t push the switch, or button for lack of a right way to say it.