Mercury 25 EFI Service Manual page 258

Cylinder Block/Crankcase
Piston Ring Side Clearance
Measure piston ring side clearance. Replace the piston and rings if out of specification.
Piston Ring Side Clearance
Top "a"
Top "a" (service limit)
Middle "b"
Middle "b" (service limit)
Oil "c"
Oil "c" (service limit)
Piston Ring End Gap
Measure the piston ring end gap clearance. Replace the piston rings as a set if out of specification.
NOTE: The ring must be level for measurement. Push the ring 4 mm (0.157 in.) into the bore with the crown of a piston.
a
Piston Ring End Gap
Top
Top (service limit)
Middle
Middle (service limit)
Oil
Page 4A-16
a
b
c
22023
a - 4 mm (0.157 in.)
22024
© 2016 Mercury Marine
a - Top ring
b - Middle ring
c - Oil ring
0.04–0.08 mm (0.0016–0.0031 in.)
0.10 mm (0.0039 in.)
0.03–0.07 mm (0.0012–0.0028 in.)
0.09 mm (0.0035 in.)
0.05–0.15 mm (0.002–0.0059 in.)
0.17 mm (0.0067 in.)
0.15–0.30 mm (0.0059–0.0118 in.)
0.50 mm (0.0197 in.)
0.35–0.50 mm (0.0138–0.0197 in.)
0.70 mm (0.0276 in.)
0.20–0.70 mm (0.0079–0.0276 in.)
90-8M0105568 eng MARCH 2016