1985 Mercury Outboard V-300 V-3.4L Shop Service Manual, Page 108Get this manual
Cylinder Bores IMPORTANT: The cylinder bores are chrome and cannot be rebored or efficiently honed(Honing 01 chrome cylinder Is not necessary or recomd Stepsb" and "c" ma require repeating seve ral times before all the al uminum deposits are gone eCh eck ea cy linder for an out-ofro und (" eggshaped") conditi on Usi ng an inside micrometer telescopic ga uge, as shown below, take measurement '1" (l2.7m m) from top of each cylinder bore 45 from each th erA .006" (O.lS2mmor less out -ofround is accepta bleIf outof.round is more than .006" ,cylinder bloc nd rankcase cove must be replacedfAfter cleani ng and inspection, ylillder bores should be swabbed se veral limes with light engine oil and clean cloth