What happened to my prop? Boat will not move

[CajunSpike]

This just happened to my E27. Found local diver on Craigslist for $175 for check out and simple fix if possible. Haven't scheduled a date yet.

[rockhopper]

Well, finally have an update. My propeller is still attached to the boat. https://youtu.be/JbRduSlsmDA about 45 seconds into the video you can clearly see the prop is still there. Will be hopefully getting it hauled out Friday to address this plus do some fiberglass repairs.

Thinking I may get the yard to drop the mast as well, not sure what condition the chainplates are in after all of these years.

[CajunSpike]

I just solved my problem..which was 100% the same as you describe. Prop does not move boat in either direction with engine in gear.

Sequence I found was this:

1) Rear half of the prop shaft coupling connects to the prop shaft by a pinch bolt thru the coupling.
2) Pinch bolt backed out. Supposed to be wired in place, was not.
3) Putting the boat in reverse, the prop shaft pulled backwards since the pinch bolt was no longer in place to hold it together.
4) Since the prop shaft pulled backwards it disengaged from the coupling key. This resulted in the motor spinning, but the prop not spinning.

My solution:
Cut work space in rear engine box to access prop shaft coupling.
Unbolt engine from floor and other necessary fittings and drag fwd a couple inches to have room to remove coupling.
Remove the old shaft coupling, finding the cause of the slippage.

New coupling on order and all gaskets to fix what I unbolted.
New key on order.

To be done:
Reinstall new coupling, wire pinch bolt in place, using new shaft key.
put engine back in place
reattach everything disconnected to move motor
pray.

[Al Schober]

Not an uncommon thing to have the shaft pull out of the coupling. Our YC launch snagged a mooring and pulled the shaft out of the coupling - it also pulled it out of the shaft seal, out of the bearings, and out of the boat! Launch operator plugged the hole in the shaft seal and had a dingy tow the launch to the beach before it sank. Yes, we recovered the shaft & prop.
Common cause is that the shaft was not drilled for the point of the set screw. These set screws are typically 5/16 diameter, and the shaft has to be drilled at least 3/16 deep to take the working end of the screw. Just snugging the set screw against the shaft and relying on friction is unsat.