Buy two cheap steel nuts at the hardware store that fit your shaft. Screw one nut on until it is finger tight against the prop. Screw the second nut on until it is not quite all the way onto the shaft. Using two wrenches tighten the first nut against the second nut. Then take a small sledge hammer (2-3 lb) and hit the second nut sharply. The idea is that hitting the nut generates harmonics in the shaft that pops the prop off. It may take 2-3 pops with the hammer, but the prop will come off. This is what I did, on advice from my local prop shop, to remove my 20"x15" three blade prop that the prop puller and heat wouldn't budge. Three good pops with my small sledge popped the prop right off. Just try to hit the nut as square to the shaft as you can. Seriously, this mothod WILL WORK. It is a variant of what is called a magic nut or harmonic puller.

One thing to avoid at all costs is hitting the prop itself. First the prop is bronze which is soft so it will absorb most of ahammer blow by deforming. Second the deformation changes the balance of the prop. Furthermore hitting the prop hub on the side may actually bend your shaft. Don't do it