1993 Johnson Evinrude "ET" 9.9 thru 30 Service Manual, P/N 508282, Page 154Get this manual
1221 9Measure the piston in two locations, 90 apart from each other,
in(3 mm) above the bottom of the piston skirt
10The difference between the two measurements is the out-ofroundness and must be no more than 0.002 in(0,05 mm)1231 11Place each ring, separately, in its respective boreUse a
piston to square the ring in the cylinderUse feeler gauge to measure the ring end gap The
(0,13-0,38 mm)