1993 Johnson Evinrude "ET" 90 degrees CV Service Manual, P/N 508285, Page 141Get this manual
1441 10Use micrometer to check piston conditionMake at least two measurements, 90 from each otherMeasure the piston diameter 14 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 0.019-0.031 in(0,480,79 mm)1461 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)r:;:;J 13Use machinist's straightedge to check clearance on the upper Pressure-Back ringsInstall each Pressure-Back ring on its pistonWhen checked with the straightedge, there should be enough ring clearance to allow the straightedge to touch the piston on both sides of the ring grooveMake several checks around the piston If straightedge does not touch piston, remove the ring and clean ring grooveAssembly