1998 Johnson Evinrude "EC" 25, 35 HP 3-Cylinder Outboards Service Manual, Page 135Get this manual
6Use OMC Cylinder Bore Gauge, PIN 771310, to inspect each cylinder bore for an out-of-round, oversize, or tapered conditionBe sure the gauge or micrometer is perfectly square in the bore when measuring
7Measure each cylinder in at least two areas as shownEach area should be measured twiceThe difference between the two measurements in each area is the cylinder out-of-round dimension The cylinder must not be out-of-round by more than 0.004 in(0,10 mm)
8The dimension difference between the two areas is cylinder taper The cylinder taper must not exceed 0.002 in(0,05 mm)
9The difference between your measurements and standard bore dimension is cylinder oversizeRefer to Engine Specifications, Section 1, for dimensions The cylinder must not be oversized by more than 0.004 in(0,10 mm)
INote If any cylinder is outside these tolerances, it must be bored
oversizeIt is permissible to have one or more oversize pistons in an engineRefer to Engine Specifications, Section 110Use micrometer to check piston conditionMake at least two measurements, 90 from each otherMeasure the piston diameter in(6,4 mm) above the bottom edge ofthe piston skirt The difference between the two piston measurements must not exceed 0.003 in(0,08 mm)