2003 Johnson ST 6/8 HP 4 Stroke Outboards Service Manual, PN 5005471, Page 145Get this manual
POWERHEAD INSPECTION Check for cylinder head warpage using piece of bar stock or machinist's straightedge and feeler gauge set Cylinder head warpage must not exceed 0.003 in(0.08 mm) per inch of measurementReplace head if warpage exceeds this dimensian
1Measurement areas
The dimensional difference between the two areas is the cylinder taper Cylinder taper must not exceed 0.002 in (0.05 mm)The difference between your measurements and standard bore dimension is cylinder oversizeRefer to TECHNICAL DATA in SPECIAL TOOLS AND SERVICE SPECIFICATIONS for dimensions The cylinder must not be oversize by more than 0.002 in(0.05 mm)
Use Cylinder Bore Gauge, PIN 771310, to inspect each cylinder bore for an out-of-round, oversize, or tapered conditionMake sure the gauge or micrometer is perfectly square in the bore when measuring
IMPORTANT: If any cylinder is outside these tolerances, it must be bored oversizeOne oversize piston is available for this engine 0.030 in(0.762 mm)To determine oversize bore, add 0.030 in(0.762 mm) to the standard boreRefer to TECHNICAL DATA in SPECIAL TOOLS AND SERVICE SPECIFICATIONSIt is permissible to have one or more oversize pistons in an engineMeasure the piston in two locations, 90 apart from each other, 18 in(3 mm) above the bottom of the piston skirt The difference between the two measurements is the out-of-roundness and must be no more than 0.002 in(0.05 mm)