Alright! Good job!
Now you need to make sure that the adjustment is correct.
You do need to turn the prop while someone else selects REVERSE gear. You do this because the shift rods move DOWN for reverse and this gives you the best access to the adjustment and jamb nuts.
The initial adjustment is done by turning the long nut so that it climbs UP the upper shift rod and AWAY from the smaller jamb nut.
When the long adjustment nut is on the verge of releasing the lower rod OR, when the two rods are uncoupled, adjust the jamb nut up or down until it is approximately 8mm (3/16") from the upper end of the lower shift rod. Lastly, turn the long nut down to meet the jamb nut trying not to change the 8mm dimension you set. When the nuts are in contact with each other, firmly snug them together using two 10mm open end wrenches.
Test the adjustment by slowly turning the prop as you move from reverse to neutral to forward gear. The prop should firmly lock in one direction. Then, repeat this while turning the prop and selecting reverse. The prop should lock in both directions. If this is how it "dry shifts" with the engine not turning, it should shift well when in actual use. If you can check it in a can full of water, that will allow you to make a "fine tuning" adjustment without interrupting an outing.
If it does need to have additional adjustment because it grinds in one gear or another, remember that if it doesn't go all the way into forward (grinds), you need to engage a little more thread on the lower shift rod by turning the long nut down. This will allow the shift linkage to slightly raise the lower shift rod for better forward engagement. Likewise, if you find she grinds in reverse, raise the long nut slightly and the linkage will push the lower shift rod DOWN for more positive reverse engagement.
On shifting in general, always change gears when the engine idling. If in forward and going to reverse, pause briefly in neutral. Do the same going from reverse to forward.
When going from the neutral pause position shift the transmission with a swift, firm motion so the transmission sort of "snaps" into gear. Slowly selecting a gear so that you can hear a chattering noise is not recommended. This will cause premature wear of the clutch.
Hope you got all that and
Good luck.