lower unit

[Monkey Butler]

Very likely to be the shift rod is wasted. Drain the lower unit and look for metal shavings. A little bit on the drain plug magnet is normal but if it chewed up a gear you should be able to tell real fast.

Replacing the shift rod is not trivial but you can do it your self if you are handy. If not it probably wouldn't be economical to pay a pro mechanic to fix it.