Speedo won't adjust

[5:00]

My speedo indicates about 50% of the speed we are actually going. I checked the paddle wheel and it is free spinning. I checked the adjustment knob and there is no stopping point in either direction. It spins either direction with no stop. Is this right?
Both the needle and PP are reading the same.
Any ideas?

[5:00]

New potentiometer on the way in time for the weekend. It would be too easy of a fix. I didn't have time to test the old one before leaving last weekend.