It's going to take a lot of grinding to get the prop hub splines over the nut....
Put the PB blaster in the hole for the lock bolt, that will get it on the main threads. Then use a 24mm socket.... Put one blade as far into its slot as you can and jam the blade with a block of wood
against the hull
bottom, then use a big breaker bar with the 24mm socket.
Or, try an impact wrench.