2006 Johnson SD 30 HP 4 Stroke Outboards Service Manual, PN 5006592, Page 156Get this manual
POWERHEAD PISTON, CYLINDER, AND CRANKSHAFT If the measurement exceeds the service limit, replace the piston andor the piston ringsPiston Ring-to-Groove Clearance 0.0012 to 0.0027 inTop (0.03 to 0.07 mm) Standard 0.0008 to 0.0024 in2nd (0.02 to 0.06 mm) 0.005 in(0.12 mm) Top Service Limit 0.004 in(0.10 mm) 2nd
If the measurement exceeds the service limit, replace the piston rings Piston Ring End Gap 0.005 to 0.011 inTop (0.12 to 0.27 mm) Standard 0.014 to 0.020 in2nd (0.35 to 0.50 mm) Top 0.028 in(0.70 mm) Service Limit 2nd 0.039 in(1 .00 mm)
1Cylinder 2Piston ring 3Thickness gauge
Piston Ring Groove Width 0.0400 to 0.0410 inTop compression ring (1.02 to 1.04 mm) 0.0476 to 0.0484 in2nd compression ring (1.21 to 1.23 mm) 0.0790 to 0.0800 inOil ring (2.01 to 2.03 mm) Piston Ring Thickness 0.038 to 0.039 inTop compression ring (0.97 to 0.99 mm) 0.046 to 0.047 in2nd compression ring (1.17to 1.19 mm)