George,
Try using an impack driver to lossen them up. Used a dirt bikes moons ago. Support under the bearing too. I forget but many later 4 cylinder mtrs will fit your motor. Go to Johns Old Mercury site for more data on swap data. Be careful, they are a click type site. I didn’t get along with some so I deleted them, not saying you might like them, Jeff didn’t is all.
You might look at those piston related bearings for pits, just to be sure it’s right.
Jeff
