Westerbeke W-46 - Pistons and Piston Rings

INSPECTION/REPAIR
Pistons and Piston_Rings
1. Pistons
Inspect each piston for any
abnormal wear of its sliding
surface; cracks at the crown
and evidence of melting or
fusion. Examine the ring ·
grooves for stepped wear and
sloped wear. Replace those
pistons found in bad condition.
2. Piston clearance in the bore.
Using a micrometer, measure
each piston at the positions
listed below and compute the
radial clearance at each posi-
tion· by referring to the bore
diameter of its sleeve deter-
mined in the previous text.
Specifications
Unit:
mm (in.)
Item
Standard
Service
limit
Standard
83.90
(3.3031)
0.25 (0.0098)
84.15 (3.3130)
Diameter
oversize
-0.2
(at skirt A) 0.50 (0.0197)
84.40
(3.3228)
(-0.008)
oversize
'
0.545 ~ 0.610
Top
(0.02146 ~ 0.02402)
Top of 2nd ring
0.425 ~ 0.490
Fit in
land
(0.01673 ~ 0.01929)
cylinders
Bottom
of 3rd
o.245
~0.310
ring land
(0.00965 ~ 0.01220)
Skirt
0.085
~ 0.150
(0.00335
~ 0.00591)
20
B
B
-+-~---~~A
--t::::._l- B