I turn the nut all the way on to the prop end of the driveshaft, it should just turn on with finger pressure, then turn the prop on the same way until it bottoms out ( reaches bottom of threaded hole in prop ). It should do this with just finger pressure, if not & it binds clean the thread with the proper size tap or die so that the prop screws on freely without binding on the thread. When the prop is on all the way you now turn the nut tight against the prop. Do NOT hold the prop with anything except your fingers, using pliers or other gripping tools to hold the prop will almost certainly damage the prop. If you install the prop in this manner you should have no trouble. Make sure you use the RIGHT SIZE spanner to tighten the nut, if you don't & you round off the corners of the nut you may a lot of difficulty getting it off later. needless to say you do not grip the drive shaft with any sharp edged tool that might damage the shaft surface, if you do this you will in all probability permanently damage the shaft causing it to leak water or worse bind in the outer tube. Any other questions just ask or PM me, I will be most happy to help you at anytime. Mick B.