I bought a 1999 Mercury outboard motor 200 HP EFI, it runs but took it out on water and it only went to 3000 rpm and then wont plane. Took it to mechanic and tested it. All the electricals are working except it showed all the cylinders were not putting out like should. So checked compression on all 6. All 5 were 90 and the bottom right side cylinder was 40. Like i said starts right up and runs just wont go over 3000 rpm and wont plane. Anyone know if it can still be fixed without rebuilding? Piston ring? Piston gasket? Etc?
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