Mercury 305 CID, Service Manual, Page: 248 / 967

3A-56 - ENGINES 90-823225--1 1096
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.
Inspection and Replacement
IMPORTANT: Before you remove the connecting
rod cap, mark the side of the rod and cap with the
cylinder number to assure matched reassembly
of rod and cap.
1. With oil pan and oil pump removed, remove the
connecting rod cap and bearing.
2. Inspect the bearing for evidence of wear and
damage. Do not reinstall a worn or damaged
bearing.
3. Wipe both upper and lower bearing shells and
crankpin clean of oil.
4. Measure the crankpin for out-of-round or taper
with a micrometer. If not within specifications, re-
place or recondition the crankshaft. If within
specifications and a new bearing is to be in-
stalled, measure the maximum diameter of the
crankpin to determine new bearing size required.
5. If within specifications, measure new or used
bearing clearances with gauging plastic or its
equivalent. If a bearing is being fitted to an
out-of-round crankpin, be sure to fit to the maxi-
mum diameter of the crankpin. If the bearing is
fitted to the minimum diameter, and the crankpin
is out of round .001 in., interference between the
bearing and crankpin will result in rapid bearing
failure.
a. Place a piece of gauging plastic, the length of
the bearing (parallel to the crankshaft), on the
crankpin or bearing surface as shown. Posi-
tion the gauging plastic in the middle of the
bearing shell. Bearings are eccentric and
false readings could occur if placed else-
where.
72361
a - Gauging Plastic
a
b. Install the bearing in the connecting rod and
cap.
c. Install the bearing cap and evenly torque nuts
to 45 lb. ft. (61 N·m).
NOTICE
Do not turn the crankshaft with the gauging
plastic installed.