1992 Johnson Evinrude "EN" 9.9 thru 30 Service Manual, P/N 508142, Page 162Get this manual
6Check piston with micrometer to determine if piston has been distorted during assemblyMeasure the piston at two places, 90 from each other, 18 to 114 in(3,2 mm to 6,4 mm) above bottom edge of the skirtIf the difference between the two measurements is greater than 0.002 in(0,05 mm), the piston is out of round or worn and must be replaced7Install piston rings on each pistonSpread each ring with ring expander just enough to slip it over the head of the piston and down into place8Coat the piston and cylinder bore with oil rav 9Place the piston in OMC Ring Compressor PIrings are corN 326590 (for standard size piston)Make certain that the
rectly positioned in their grooves with respect to the dowel pinsDamaged pistons and broken rings may result from imperfect alignment of the ring gap and the dowel pinsThe piston rings must be correctly located on their dowel pins to prevent permanent powerhead damage1321 10Start the piston into bore ofthe cylinder with deflector of the piston (sharp edge) toward intake port side of the cylinder block