Can Not Put Boat Into Gear

With the engine off, are you able to disconnect the trans shift cable at the trans end, and get the trans to shift into forward and reverse by hand? If yes, I would start tracking the problem to the front of the boat.

I would next try shifting the boat into gear with the cable still disconnected at the trans to see if the cable moves. If the cable moves freely, your Morse control may be jammed/broken somehow.

I just put my Morse control back in over the weekend. Not a fun task, and you can't see what you are working on. You have to do everything by feel. Maybe one of the levers became disconnected??

Just some thoughts to try and point you in the right direction.