Cylinder Block - MerCruiser GM4 Service Manual

Cylinder Block

Cleaning and Inspection
1. Remove all engine components as previously
outlined.
2. Wash cylinder block thoroughly in cleaning sol-
vent and clean all gasket surfaces.
3. Remove oil gallery plugs and clean all oil pas-
sages.
4. Remove expansion plugs.
NOTE: These plugs may be removed with a sharp
punch, or they may be drilled and pried out.
5. Clean and inspect water passages in cylinder
block.
6. Inspect cylinder block for cracks in cylinder walls,
water jacket valve lifter bores and main bearing
webs.
!
CAUTION
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 de-
termine taper and turn it to different points
around cylinder wall to determine out-of-round
condition. If cylinders exceed specifications, bor-
ing and/or honing will be necessary.
Index
3A - 44 - ENGINES
"A" = At right angle to centerline of engine
"B" = Parallel to centerline of engine
"Out-of-Round" = Difference between "A" and "B"
"Taper" =Difference between measurement "A" at top of cylin-
der bore and "A" measurement at bottom of cylinder bore
Cylinder Measurement
Measuring Cylinder Bore With Snap Gauge
72385
72386
90-816462 2-695