Likely one screw fell out of the shift rod connecter.----Take out 6 screws.----Drop the lower unit down and have a look in there.
Isn't there a cover he can remove that is on the side of the motor to take a look at the shift rod connector on this motor? If not, that connector must be farther down into the lower unit, correct?
iggyw1-----Not all motors are the same.-------Not all posters here have the same level of experience.