2002/2003 Johnson SN/ST 2 Stroke 3.5, 6 8 HP Outboards Service Manual, PN 5005466, Page 157Get this manual
POWERHEAD ASSEMBLY68 Check piston with micrometer to determine if piston has been distorted during assemblyMeasure the piston at two places, 90 from each other, 18 to 14 in(3 mm to 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 outof-round or worn and must be replacedInstall piston rings on each piston Spread each ring with ring expander just enough to slip it over the head of the piston and down into placeStart the piston into bore of the cylinder with deflector of the piston (sharp edge) toward intake port side of the cylinder block
IMPORTANT: Loosely install the cylinder head