Mercury MerCruiser MCM 454 Mag MPI Service Manual page 286

454 CID (7.4L) / 502 CID (8.2L)
3. Measure cylinder walls for taper, out-of-round or excessive ridge at top of ring travel.
This should be done with a dial indicator or inside micrometer. Carefully work gauge up
and down cylinder to determine taper and turn it to different points around cylinder wall
to determine out-of-round condition. If cylinders exceed specifications, boring and/or
honing will be necessary.
Cylinder Measurement
"Out Of Round" Equals The Difference Between "a" and "b"
Measuring Cylinder Bore With Telescope Gauge
Measuring Cylinder Bore With Dial Indicator
Index
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a - At Right Angle To Centerline Of Engine
b - Parallel to Centerline Of Engine
Measurement At Top Of Cylinder Bore and
Measurement At Bottom Of Cylinder Bore
a
b
b
a
SERVICE MANUAL NUMBER 23
72385
72570
72569
90-861326--1 MARCH 1999