Can’t get impeller off shaft

Need to replace the impeller on my Merc 135 and I can’t get the old one off. Any ideas?

Turn it backwards to rotation, will come right off as it is wedged in the direction of rotation now.

used a chisel to get it off the shaft put it back together and pump worked great…but now have to take it back apart to get the transmission right. put it in gear and prop spins freely done for the night but have to be close. (I hope). Now I remember why I always paid a professional to get it done.

Sounds like the tranny and gear selector were not in the same positions. Having both in neutral seems to be the easiest when the linkage is splined. Double check operation before you tighten all bolts down.
If you always take stuff in to get worked on you will never become any smarter.

I think my last service was $80.00 to get that done. money well spent in my opinion.

All fixed. Since it was $50 for the kit at $80 for the service it would have been worth it. Thank you for the help to those who offered. Watched a video where the guy used a ratcheting strap to help hold the lower unit and it makes a huge differance