First of all, welcome to iboat. We like having new folks join us... :welcome:
Does the "grinding" sound come from the actual foot (motor) section? If so it could be time for new brushes, or bearings and seals and such. There really isn't much else in the motor foot section but the armature, brushes and brush holder, and of course bearings and seals. And all those things are still available. If not from the actual manufacture, certainly from after market parts. Most brushes, bearings and seal are standardized. Trolling motor manufacture will use off-the-shelf standardized bearings and seal to keep manufacturing cost down. So those shouldn't be too hard to find, if needed... Let us know about where the sound is coming from. You can also manually turn the prop by hand (but not connected to power) and feel if it is grinding. That will tell you for certain if there is any problems. You should only feel the magnet pull as you rotate the prop. Any grinding or excessive endplay in the prop shaft, and that IS your problem. JMHO!