Mercury Mariner 4 and 5HP 4-Stroke Outboards Service Shop Manual 1999, Page 146Get this manual
CYLINDER BLOCK AND CRANKCASE
Measuring Piston Ring End Gap
Standard Value Out of the Limit If 0.020 in(0.5 mm) or more requires replacement If 0.028 in(0.7 mm) or more requires replacement If 0.024 in(0.6 mm) or more requires replacement
0.0060.014 in(0150.35 mm) 0.0120.020 in(0.300.50 mm) 0.0080.016 in(0.200.40 mm)
Push piston rings into cylinder approximately 0.8 in(20 mm) deepPu sh in the rings using the piston