2 part questions thermostat and steering

[SkunkBoat]

First step is disconnect link arm.

That isolates problem to either the cable or the pivot shaft of the motor (or possibly both)

If its the cable, you should be able free it up by cleaning and greasing when extended out of the port side of the motor.
You should be able to turn the wheel with your pinky finger. If you can't, then the cable is binding inside of the black plastic sheath....buy a new one...
Disconnecting the starboard side nut is not going to do anything unless you get the whole cable out. That will let you clean out old grease better.

If the motor does not turn easily by hand with the link arm disconnected from the cable, you need to grease or clean & regrease the pivot shaft.

My pivot shaft has been giving me some trouble. new grease was not pushing out old grease so the grease gun was "pressurizing " the shaft making it even harder to turn. I took out the zerk fitting and it shot grease out the hole! That made it easier to turn but not great. I sprayed WD into the hole and top/bottom and moved it back&forth alot. That loosened it up "good enough to go fishing". In the spring I will probably pull the motor and disassemble and clean the pivot. I remember when my motor was new that thing was smooth and really easy to turn by hand, even with cable attached.