Mercury 305 CID, Service Manual, Page: 245 / 967

ENGINES - 3A-53 90-823225--1 1096
When a production crankshaft cannot be precision
fitted by this method, it is then ground .009 in. under-
size ON ONLY THOSE MAIN JOURNALS THAT
CANNOT BE PROPERLY FITTED. ALL JOURNALS
WILL NOT NECESSARILY BE GROUND UNDER-
SIZE. A .009 in. undersize bearing and .010 in. un-
dersize bearing may be used for precision fitting in
the same manner as previously described.
Inspection
In general, the lower half of the bearing (except
No. 1 bearing) shows a greater wear and the most
distress from fatigue. If, upon inspection, the lower
half is suitable for use, it can be assumed that
the upper half is also satisfactory. If the lower half
shows evidence of wear or damage, both upper
and lower halves should be replaced. Never re-
place one half without replacing the other half.
Checking Clearances
To obtain accurate measurements while using Plasti-
gage, or its equivalent, engine must be out of the boat
and upside down so crankshaft will rest on the upper
bearings and total clearance can be measured be-
tween lower bearing and journal.
To assure the proper seating of the crankshaft, all
bearing cap bolts should be at their specified torque.
In addition, preparatory to checking fit of bearings,
the surface of the crankshaft journal and bearing
should be wiped clean of oil.
1. With the oil pan and oil pump removed, remove
bearing cap and wipe oil from journal and bearing
cap to be inspected.
2. Place a piece of gauging plastic the full width of
the bearing (parallel to the crankshaft) on the
journal as shown.
72357
a - Gauging Plastic
b - Journal
b
a
NOTICE
Do not rotate the crankshaft while the
gauging plastic is between the bearing and
journal.
3. Install the bearing cap and evenly torque the re-
taining bolts to specifications. Bearing cap MUST
be torqued to specification in order to assure
proper reading. Variations in torque affect the
compression of the plastic gauge.
4. Remove bearing cap. The flattened gauging
plastic will be found adhering to either the bearing
cap or journal.