Installation; Main Bearings; Inspection; Checking Clearances - Mercury MerCruiser MCM 454 Mag MPI Service Manual

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SERVICE MANUAL NUMBER 23

Installation

1. Apply Quicksilver Perfect Seal to engine block/seal mating surface. Apply grease to seal

2. Install seal using rear main seal installer or suitable device.

IMPORTANT: Before removing main bearing caps or connecting rod caps, mark them

for reassembly in their original locations.

Main bearings are of the precision insert type and do not use shims for adjustment. If

clearances are found to be excessive, a new bearing, both upper and lower halves, will be

required. Service bearings are available in standard size and .001 in., .002 in., .010 in. and

.020 in. undersize.

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 replace one half without

replacing the other half.

To obtain accurate measurements while using Plastigage, or its equivalent, engine must be

out of the boat and upside down so crankshaft will rest on the upper bearings and total clear-

ance can be measured between 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.

IMPORTANT: Inspect bearing caps for orientation marks prior to removal. If no mark-

ings exist, make suitable marks before disassembly so that they can be reinstalled

in their original locations.

1. With the oil pan and oil pump removed, make suitable marks, if required, on bearing

90-861326--1 MARCH 1999

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Suitable Device Shown (Rear Main Seal Installer J-38841 Not Shown)

cap(s) to be inspected. Remove bearing cap(s) as needed. Wipe oil from journal and

bearing cap to be inspected.

454 CID (7.4L) / 502 CID (8.2L)

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