woko said..
Start it up drop it in gear an see if the shaft is turning, then you'll be able to deduce if it's the transmission or the prop. My guess a broken Morse cable
Selling a small yacht I had years ago, bringing her from the swing mooring to a marina to collect the potential buyers, approaching the berth (buyers watching on the dock) I put her into neutral and she didn't slow down so into reverse still didn't slow down and I was running out of room so I gave it a burst of power to stop the boat and she lurched forward and straight into the floating berth.
The bolt holding the morse cable to the gear selector has dropped off and she was still in forward.