With all the top rings broken I'd suspect detonation or improper ring fitting on install. How did the pistons look? Were there pieces broken away above the rings?
Pistons looked decent to me. No breaks or anything. They looked to my untrained eye to be "normal" (only carbon on the tops of them) I'll snap some photos of the damage this weekend and post them. The motor was in the boat when I got it last year so who knows if they were correctly installed...