Step one
Move the shifter at the helm into full throttle IN gear (F) position this moves the shift rod connector out of the way of the top of the shift rod. Note you will need to position the rod once in place and ease her back into the N position to connect the rod screw.
Step 2
Check the water pickup tube in the mid section you may have twisted it out of position.
Step 3
Push the shift rod DOWN to engage the LU in gear, you will need the second person to slowly turn the prop or flywheel in a clockwise rotation it whilst you push the LU up into place (this is to engage the splines)
To look for Water Pickup Tube, Spline engagement and Top of shift rod also the exhaust adapter..
Hopefully this helps..
Here is a photo of the shift rod through the hole and connected on my 87 140 v4
Picture of the water pickup tube (picture taken with the mid upside down)
Good Luck