1998 Johnson Evinrude "EC" 9.9 thru 30 HP 2-Cylinder Outboards Service Manual, 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)
12311 1Place 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)