454 CID (7.4L) / 502 CID (8.2L)
SERVICE MANUAL NUMBER 23
Page 3A-16
90-861326--1 MARCH 1999
General Information
Some of the repairs in this section must be completed with engine removed from boat.
Engine removal depends upon type of repair and boat design. Place engine on repair stand
for major repairs.
When engine removal is not required, make certain that battery cables are disconnected
at the battery prior to performing any on-board repair procedures.
Lubricate all moving parts (during reassembly) with engine oil. Apply Quicksilver Perfect
Seal on threads of and under heads of cylinder head bolts, and on threads of all cylinder
block external bolts, screws and studs.
Engine Identification
The MerCruiser Model can be determined by looking at the last two letters of the engine
code stamped into the cylinder block. This code number is stamped on all MerCruiser power
packages and replacement partial engines, but not replacement cylinder block assemblies.
If the engine serial number and/or model decals are missing, the engine code letters may
help in determining the engine models. Following is a list of GM engines and their respective
code letters.
72312
a
a -
Location Of GM Engine Code
MCM (Sterndrive)
Code
Rotation
7.4L MPI
XW
454 Mag MPI
UA
LH
502 Mag MPI
HJ
MIE (Inboard)
Code
Rotation
7.4L MPI
XY
454 Mag MPI
UF
LH
8.2L
HH
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