MerCruiser 13, Service Manual

Page: 120 / 348

3A - 30 - ENGINES 90-816462 2-695
5. On the edge of the gauging plastic envelope there
is a graduated scale which is correlated in thou-
sandths of an inch. Without removing the gauging
plastic, measure its compressed width (at the
widest point) with the graduations on the gauging
plastic envelope as shown.
72358
b
a
a - Compressed Gauging Plastic
b - Graduated Scale
NOTE: Normally main bearing journals wear evenly
and are not out of round. However, if a bearing is be-
ing fitted to an out-of-round journal (.001 in. max.), be
sure to fit to the maximum diameter of the journal: If
the bearing is fitted to the minimum diameter, and the
journal is out of round .001 in., interference between
the bearing and journal will result in rapid bearing fail-
ure. If the flattened gauging plastic tapers toward the
middle or ends, there is a difference in clearance indi-
cating taper, low spot or other irregularity of the bear-
ing or journal. Be sure to measure the journal with a
micrometer if the flattened gauging plastic indicates
more than .001 in. difference.
6. If the bearing clearance is within specifications,
the bearing insert is satisfactory. If the clearance
is not within specifications, replace the insert. Al-
ways replace both upper and lower inserts as a
unit.
7. A standard, or .001 in., undersize bearing may
produce the proper clearance. If not, it will be nec-
essary to regrind the crankshaft journal for use
with the next undersize bearing.
8. After selecting new bearing, recheck clearance.
9. Proceed to the next bearing. After all bearings
have been checked, rotate the crankshaft to see
that there is no excessive drag. When checking
No. 1 main bearing, loosen accessory drive belts
so as to prevent tapered reading with plastic
gauge.
Main Bearing Replacement
1. Remove and inspect crankshaft.
2. Remove main bearings from cylinder block and
main bearing caps.
3. Coat bearing surfaces of new, correct-size, main
bearing with oil and install in cylinder block and
main bearing caps. Check clearance.
4. Install crankshaft.
5. Torque all main bearing caps, EXCEPT THE
REAR MAIN CAP, to 75 lb. ft. (102 N·m). Torque
rear main bearing cap to 10-12 lb. ft. (14-16 N·m);
then tap end of crankshaft, first rearward then for-
ward with a lead hammer. This will line up rear
main bearing and crankshaft thrust surfaces.
Torque rear main bearing cap to 75 lb. ft. (102
N·m).
Connecting Rod Bearings
Connecting rod bearings are of the precision insert
type and do not use shims for adjustment. DO NOT
FILE RODS OR ROD CAPS. If clearances are found
to be excessive, a new bearing will be required. Ser-
vice bearings are available in standard size and .001
in. and .002 in. undersize for use with new and used
standard size crankshafts, and in .010 in. and .020 in.
undersize for use with reconditioned crankshafts.
On removing a connecting rod cap, it is possible to
find a .010 in. undersize bearing. These are used in
manufacturing for selective fitting.