Mercury MerCruiser MCM 454 Mag MPI Service Manual page 276

454 CID (7.4L) / 502 CID (8.2L)
6. Clean and inspect pistons, if not previously done.
7. Install piston rings as follows:
a. Install oil ring spacer in groove and insert anti-rotation tang in oil hole.
b. Hold spacer ends butted and install lower steel oil ring rail with gap properly located.
c. Install upper steel oil ring rail with gap properly located.
d. Flex the oil ring assembly to make sure ring is free. If binding occurs at any point,
IMPORTANT: Use piston ring expander (91-24697) for compression ring installation.
e. Install lower compression ring with marked side up, using ring expander.
f.
Installation
IMPORTANT: Cylinder bores must be clean before piston installation. Clean with a
light honing, as necessary. Then clean with hot water and detergent wash. After
cleaning, swab bores several times with light engine oil and clean cloth, then wipe
with a clean dry cloth.
1. Lubricate connecting rod bearings and install in rods and rod caps.
2. Lightly coat pistons, rings and cylinder walls with light engine oil.
3. With bearing caps removed, install connecting rod bolt guide (3/8-24, use tool J-5239
or 7/16-20, use tool J-35228) on connecting rod bolts.
IMPORTANT: Be sure ring gaps are properly positioned as shown.
Ring Gap Location
Index
Page 3A-72
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the cause should be determined and, if caused by ring groove, removed by dressing
groove with a fine cut file. If binding is caused by a distorted ring, use a new ring.
Install top compression ring with marked side up, using ring expander.
e
a - Oil Ring Spacer Gap (Tang In Hole Or Slot Within Arc)
b - Oil Ring Gaps
c - 2nd Compression Ring Gap
d - Top Compression Ring Gap
e - Port Side
f - Engine Front
g - Starboard Side
f
b
c
a
d
b
SERVICE MANUAL NUMBER 23
g
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90-861326--1 MARCH 1999