1997 Johnson Evinrude "EU" 9.9 thru 30 2-Cylinder Service Manual, P/N 507263, Page 149Get this manual
9Measure the piston in two locations, 90 apart from each other, Va in(3 mm) above the bottom of the piston skirt10The difference between the two measurements is the out-ofroundness and must be no more than 0.002 in(0,05 mm)
2311Place 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 gap must be within 0.0050.015 in(0,13 0,38 mm)22
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 (0,10 mm)must not exceed 0.004 in