2006 Johnson SD 30 HP 4 Stroke Outboards Service Manual, PN 5006592, Page 155Get this manual
POWERHEAD PISTON, CYLINDER, AND CRANKSHAFT Pistons and Rings Two oversize piston and piston ring components are availableOversize pistons and piston rings are marked as shown belowPiston Oversize 10 Mark Oversize Oil Ring 10 Mark
0.25 mm 0.50 mm
Two blue marks Red mark
0.25 mm 0.50 mm
JD markoil ring
Inspect the pistons for faults, cracks, and other damageReplace any damaged pistons110 markpiston