Propeller Lock Yamaha PRO 50 HP Motor Problem?

Yamaha PRO 50 HP motor problem? - propeller lock

The motor is blocked and does not move the propeller in neutral position. When moving the wheel will eventually start up and run fine for a while, then opens and closes again. I have a manual for it. I try to see how difficult it is to fix and what will that do to speed up the proceedings? Please help me.