Port throttle will not move when in forward. Both operate together fine in neutral and reverse, but when shift lever in forward the port throttle won't move
If the lever physically wont move... then pull the lever unit out of the hull, and clean/grease it. There should be a lock out for the shifter, so you don't change direction while the throttle is up... but that same lock out could be jamming the throttle lever.
That didn't do it. But upon further inspection I noticed the rod that actuates the reverse gate on the starboard side is bent. Right where the shift lever get very stiff and difficult to move further forward is where that bent rod tries to enter the cable housing. I'm guessing that has a great deal to do with it.