I have difficulty unscrewing the propellor nut from the crankshaft, so I can install the propellor and spinner. The crankshaft keeps spinning when I try to unscrew the prop nut. I used the wrench, which is used to screw in the glowplug head. How do I unscrew the prop nut from the crankshaft? Thanks.

Sometimes I use a small pair of chanel locks to hold the shaft while I unscrew the prop nut. Hope this helps. Loren

What Engine?

i saw a guy at my LHS use a pair of channel locks to do it, but he used a peice of fabric(i think it was flannel) to stop the pliers from gouging the shaft.

you could try that. good luck.

wait a minute, i think it was vise grips come to think of it.
well i'm sure either would work.

azmuth made a good point, make sure you put something between the channel locks and the shaft!

Mike

Sometimes if you grab the prop and cock it to one side to bind the crankshaft you can break them loose that way too. If you are going to use a pair of channel locks, do protect the thrust washer or you will leave teeth marks in it, voice of experience!!

I'm a little confused here...are you saying that with no prop the nut is so tight the crank turns? Is this a locking nut (nylock or similar)? If it's just an ordinary nut then you've got a big thread problem (or Loctite ).
Try using a normal spanner on the nut but treat the spanner like a prop when hand starting..in other words give it a sharp jerk against compression. This should move even a locking nut bit by bit. You could also deliberately hydraulic lock the engine (inverted of course) but if you're not too sure about the relative strength of rods etc I wouldn't really advise this.

*Note to Americans...

Spanner = Wrench

I use the OS Engine Max-40LA.

and Canadians

Have you made any progress yet