Yamaha Outboard F15A F9.9C, FT9.9D F15 Service Manual, Page 262Get this manual
CRANKCASE AND CRANKSHAFT
2Measure: Side clearance Out of specification Replace the piston and piston rings as setSide clearance: Top ring0.0130.035 mm (0.00050.0013 in) 2nd ring0.020.04 mm (0.0010.002 in)