1984-1986 Mercury Force 9.9 and 15HP Outboards Service Manual, Page 53Get this manual
BReplace cylinder block if wear is more than .002" (0.05 mm) or if cylinder is out of round CIf cylinder Is within wear tolerance, but slightly scoredhone with line stone cylinder honeFigure 25 BCheck connecting rodsMeasu re both ends of connecti ng rod with inside icrometer
Assemble caps on rods Torque to specifications to establish proper iameter9Check pistonsAClosely inspect pistons for lack of roundnesSwear, and scoring
Use low rpm drill with rapid up and down motion to obtain good cross hatch pattern for all retentionDIf cylinder walls are glazed, break the glaze by honing with medium stone (220 grit)
The type of damage helps determine the cause: diagonal wear is not normalnew piStons can be damaged quickly in the same wayScoring can be caused by overheatingincorrect gnition timing, incorrect clearances between piston and cylinder andlor improper break-in procedureBMeasure piston at right angle to piston pinCheck for wear attop land and skirtCMeasure piston pin bore with an inside micrometer10Measure piston ring gap: AInsert new piston ring in cylinder just above exhaust port and intake portsFigure 26