Re: '71 Merc 650 reverse locking cam
On my '65 Merc Mark 1000, the reverse locking lock arm holds on to the trim pin. You might be able to remove the trim pin and pull it out and then be able to move the motor to high tilt, etc.
I'm sure you've tried having someone lift the motor up slightly while you try to push the lock up manualy on the motor? I would use a long screwdriver and keep my fingers clear of anything just in case the person lifting slightly lets go for some reason.
The cam is attached to the splines of the shift shaft, so if the shift shaft is turning (the motor can go in and out of gear), the cam should be turning. To truly get at it, you will need to remove the lower unit, if yours is set up the same way mine is. Either way, getting the motor up and on high tilt will allow you to see whats going on. Has it worked in the past?
