Tubs has a video about this on Youtube. I think a lot of tapping did save a seized piston ring if I remember correctly. I’ve read that a different approach to this is to run the motor with the stuck rings and they should free up, but this is not a reccomendation as I haven’t tried it. Just providing ideas.
I do have a video from 10 years ago removing a ring from a Rowboat Motor piston. Here is the link. https://www.youtube.com/watch?v=fWMUDYfhqW0&t=28s While I was 100% successful removing these 3 rings, rings become thinner in years to come. My percentages on the thinner rings is slightly above “O” when they are stuck like the one in my video.
A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.