Mercury Mariner 4, 5, and 6HP 4-Stroke Factory Service Manual, Page 154Get this manual
CYLINDER BLOCK AND CRANKCASE
Inspection
Measuring Cylinder Bore
1Measure the cylinder bore diameter "d" at three locations in both and axis2If the cylinder bore is beyond the limits listed in the tables below, it will be necessary to bore or replace the cylinder blockStandard Value 2.323 in(59.00 mm) 0.020 in(0.50 mm) Oversize 2.343 in(59.50 mm) Out of the Limit If 2.326 in(59.07 mm) or more, cylinder can be bored to accept oversize piston If 2.345 in(59.57 mm) or more, cylinder block needs replacementd d