1998 Johnson Evinrude "EC" 90, 115 SPL Service Manual, P/N 520209, Page 146Get this manual
10Use micrometer to check piston conditionMake at least two measurements, 90 from each otherMeasure the piston diameter 1J4 in(6,4 mm) above the bottom edgeRefer to Engine Specifications, Section 1, for piston dimensions The difference between the two piston measurements must not exceed 0.004 in(0,10 mm)
11For new or used ring sets, make the following inspectionsPlace each ring, separately, in its respective boreUse piston to square the ring in the cylinderUse feeler gauge to measure the ring end gap
The ring end gap must be within 0.0190.031 in(0,480,79 mm)
12Use feeler gauge to check groove side clearance on the lower, square ringsInstall each square ring on its pistonWith the ring seated in its groove, make several checks around the piston The side clearance must not exceed 0.004 in(0,10 mm)