I dissassembled my old power head after taking clams advice to rebuild and keep for a spare. #1 cyl. only had 50# psi. The rings were stuck in the groves except where the ring gap ends leaving the sharp end scraping the wall. I think you can only bore .015 over. This cyl. has at least a 1/16" scrape. Can these blocks be resleeved or would it be cheaper to find another block. What would cause this problem[ lack of decarbonizing maybe?]. I have another power head and waiting on a gasket to arrive to reassemble everything. so far I have spent $900.00 for parts so I can't stop now, anyway its more or less a hobby of mine to rebuild older car engines and i always liked the older inline 6 cyls. I spent a lot on the 50 hp force that I had but maybe with this merc. I won't be the laughing stock at the lake... Thanks