mercury 200 20hp won't go into reverse

[fishfeatures]

'79 200 20hp, after i changed the water pump in it, the gearbox has been going me issues. the shift shaft will turn if i put vice grips on it and the prop will turn if i turn the drive shaft.
however once i attach the lower unit , the selector on the motor won't shift into reverse, reverse gear is now neutral.

I noticed the the reverse lock wire? was out of place so i put that back in correctly so when the cam moves the wire moves too, but still reverse gear won't engage.
when i start the motor it also won't start as neutral is now in forward gear...
i'm a bit puzzled , is there a chance that where the shift rod mates with the cam in the midsection, that this is worn ? could this cause the issue or should o pull apart the gearbox??

 

[racerone]

Do this.--Remove the gearbox.---Put the lower unit in neutral.--Put lever on the motor in neutral.--Reassemble.---Sounds like the lower unit jumped to forward while you had it on the workbench.

 

[fishfeatures]

I tried that but didn't work.
now after playing with the shift shaft some more, if I put it in frwd-neut-rev, the prop will move in the correct direction if i manually turn the drive shaft. Once I reattach the lower unit, and shift through the gears it will engage them all but when it is put into reverse it now won't come out of reverse. I def think where the shift shaft mates halfway up the leg , that piece that the splines on the shift shaft slide into is worn. Do i have to remove the powerhead to inspect this part???