I presume (dangerous to assume) you have a cable driven TM. If so, take the top cover off the head of the TM. It is a pretty simple rack and pinion type mechanism. I would guess either the rack gears or the pinion gear that is on the TM shaft have stripped, or the cable itself has broken. First thing to look at is the cable connection at the foot pedal and make sure the cable is still connected to the pedal, then go to the head of the TM. Should not be too difficult to fix, unless you are looking for and excuse to buy a new one, then it is impossible to fix.
SeaRay