That damage is likely caused either by some foreign body getting into the combustion chamber or severe overheating of the piston while running. The aluminum is actually swaged over the ring. I’m just fixing a similar problem that was caused by a reed valve breaking off and getting into the piston travel area. I got the rings out of the groove but it takes patience and time because you have to convince the aluminum that it wants to move enough to let the ring go free. I kept tapping t he opposite side of t he ring with a piece of hardwood until the ring started working its way through the aluminum obstruction.
All that being said, I’d suggest you split the crankcase and look at your reeds just to make sure. You can risk it, of course, and leave t he crankcase alone, that’s your call. I’m not that good on Merc part interchange but I believe you could swap a KF7 piston in there, and that you CAN do without splitting the crankcase. Hopefully somebody who knows merc part interchange better than I can interject if I’m off base.
Best
PM T2
He's livin' in his own private Idaho..... I hope to go out quietly in my sleep, like my grand-dad did..... and not screaming, like the passengers in his car...
