I have a foot control as well as a remote control on my riptide saltwater 55 bow mount the trolling motor acts the same way with either on I use. It will not run in but 1 speed and that is in the lower speed. I have replaced the battery, (it was bad) I have checked my connections and wiring, I suspect it is in the control board??

Boating - Minn Kota - Riptide St Saltwater 55 Bow Mount Trolling Motor