can't change gears

I have just acquired boat with a OMC 4.3 Cobra. Took it to water to test everything out, and would barely go into forward or reverse (binding in controller was pretty bad). Once I did get it into reverse it stuck there, had to turn boat of to get it out of gear. After a little testing, Drained oil and removed outdrive. Once outdrive was removed, all controls on boat worked smooth as silk. Pretty sure it not any of the control cables. Tried to manually change gears in outdrive by pushing the gear changing lever up and down by hand with no luck. Could someone tell me if there is something seriously wrong with this outdrive, if so what it is so I can get closer to getting it fixed.

year ?

Was told 1980 to 1985. Not for sure how to tell for sure. Since post have worked the lever a bit and is now reluctantly going into gears, fwd and rev. Not for sure if it is supposed to go smoothly or not. That is still by hand inside actual outdrive, with it being removed from boat.