I know this thread is super old, however I just purchased a 92 TrailBoss from a buddy and am trying to replace the water pump seal and can't seem to get this slit nut off that is mentioned in this thread. I have tried using a punch but it won't budge.Sorry if this is stupid but part of my problem is finding a way to keep the crankshaft from rotating while I punch the nut, any suggestions? Am I missing something obvious? Thanks for your help if you see this.

 

You can thread some rope into cylinder through spark plug hole to take up compression space worked for me if you got cylinder head off stuff some rags on top of piston put head back on rags will stop piston