Connecting Rod Bearings; Inspection And Replacement - MerCruiser 305 CID (5.0L) Service Manual

5.0l / 305 cid / 5.7l / 350 cid ENGINES

Connecting Rod Bearings

Connecting rod bearings are of the precision insert type and do not use shims for adjust-
ment. DO NOT FILE RODS OR ROD CAPS. If clearances are found to be excessive, a new
bearing will be required. Service bearings are available in standard size and .001 in. and
.002 in. undersize for use with new and used standard size crankshafts. They are also avail-
able in .010 in. and .020 in. undersize for use with reconditioned crankshafts.
When removing a connecting rod cap, you may 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. Remove oil pan and oil pump.
2. Remove connecting rod cap and bearing.
3. Inspect bearing for evidence of wear and damage. Do not reinstall a worn or damaged
bearing.
4. Wipe both upper and lower bearing shells and crankpin clean of oil.
5. Measure the crankpin for out-of-round or taper with a micrometer.
a. Not within specifications, replace or recondition the crankshaft.
b. Within specifications and a new bearing is to be installed, measure the maximum
NOTE: If within specifications, measure new or used bearing clearances with gauging plas-
tic or its equivalent. If a bearing is being fitted to an out-of-round crankpin, be sure to fit to
the maximum 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 re-
sult in rapid bearing failure.
6. Measure bearing clearances.
a. Place a piece of gauging plastic, the length of the bearing (parallel to the crankshaft),
b. Position the gauging plastic in the middle of the bearing shell. Bearings are eccentric
Index
Page 3A-64
diameter of the crankpin to determine required bearing size.
on the crankpin or bearing surface as shown.
and false readings could occur if placed elsewhere.
a - Gauging Plastic
a
SERVICE MANUAL NUMBER 24
72361
90-861327--1 OCTOBER 1999