I cannot believe I am reading this, if you dont understand the engineering theory of a tapered, keyed, fixing method then you shouldnt be trying to remove and fit props!
sorry for being so blunt but there we are. as for the others proposing all sorts of ways to do it, listen up.
A tapered shaft and prop should already be good enough to mate. make sure the tapers are clean and the key is in place and slide the prop on. put the locking washer on and then the nut, tighten up as hard as you can (assuming a 25mm shaft) with a socket and breaker bar. this will push the tapers together so that the prop taper expands and locks on to the shaft, tap the locking tab over and that is it. if you have a castellated nut then tighten it until one of the holes lines up and put the split pin in. If you have a cone anode put this on (it has nothing to do with keeping the prop on!!) and fill the hole behind the fixing screw wit some silicon to stop the screw falling out.
To take off, take off the anode, knock back the locking tab, undo the nut a few turns, and then get your 3 legged puller and put it on, tighten the puller as tight as you can and then twat the end of the puller jacking screw and the prop will jump off, it is now that you realise why we didnt take the nut off all the way, it stops the whole caboodle from falling on your toes!
The whole idea of the key and taper method is that the taper holds the bits together, the nut is just a device to make the connection and as a safety back up.
(in the olden days I used to work on diesel electric locos, the electric motor pinion which transmitted the 500 or so hp was actually a taper fit inside the shaft, it was fitted by using hydraulic pressure and then backed up with a 1" stud, the taper did all the work.
I suspect that your gori was being held on by just the taper!
Stu