1984-1986 Mercury Force 4HP Outboards Service Manual, Page 46Get this manual
Replace cylinder block if wear is greater than 0.002" (0.05mm) or if Ihe cylinder is out of roundBIf cylinder is within wear tolerance, but slightly scored, hone lightly with fine stone cylinderFig ure 23Measure crankshaft for wear NOTE
Assemble cap on rod (matched sel) and torque to specifications to establish proper diameter8Measure both ends of the connecting rods with an Inside micrometerCompare value with specifications and replace if necessary9Check pistonAInspect piston for roundnessexcessive wear and scoringDamage should be carefully examined to determine the causeFor example diagonal wear pattern Is not result of normal wear and If the cause is not correctednew parts can be damaged in short time Pisto scoring can be caused by overheatingIncorrect ignition timing, incorrect piston to cylinder clearances andlor improper break-in procedureMeasure piston pin bore with an inside micrometer
10Measure ring gapSee Specifications section Figure 23Honing CylinderInsert new piston ring In cylinder just above exhaust port and intake ports