1998 Mercury 9.9/15HP 4-stroke outboards factory service manual, Page 200Get this manual
CYLINDER BLOCKCRANKCASE
Cylinder
1Inspect: Water jacket for mineral depositscorrosion, clean if necessaryInner surface for score marks, repair if necessary
2Measure bore diameter with cylinder gauge, re-bore or replace if necessary
NOTE: Measure at three locations (L1L2and L3in both and axis (D1-6 )L1 =0.8 in(20 mm) L2 =1.6 in(40 mm) L3 =2.4 in(60 mm)