Steve, from your first post in this thread....
There is a hub that slips over the shaft with set screws so as to accommodate a larger prop hole.
If the hub that came with the motor has two longer set screws that stick out then what you've got is a "prop saver" hub. It's something that only works on smaller electric motors. To use it you fit the hex hole over the bump on the nose of the adapter and then use a couple of small "O" rings around the blades and around behind the set screws to rubber band the prop to the adapter.
You may find that you need to somewhat drill out the hex portion for this to work.
At least if there's no obvious way to fit the prop to your adapter that came with the motor then I suspect this is what you've got.