Yamaha Outboard F15A F9.9C, FT9.9D F15 Service Manual, Page 258Get this manual
CRANKCASE AND CRANKSHAFT
SERVICE POINTS
Cylinder inspection 1Measure: Cylinder bore Out of specification Rebore or replace the cylinderNOTE:
40 mm (1.6 in)
10 mm (0.4 in)
Measure the cylinder bore in parallel and at right angle to the crankshaftThen, average the measurementsD1 and 2
70 mm (2.8 in)