Mercury 305 CID - General; Engine Identification

ENGINES - 3A-1590-823225--1 1096
General
Some of the repairs in this section must be completed
with engine removed from boat. Engine removal de-
pends upon type of repair and boat design. Place en-
gine on repair stand for major repairs.
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 deter-
mining the engine models. Following is a list of GM
engines and their respective code letters.
72312
a
a - Lcation Of G.M. Engine Code
MCM (Stern Drive) Code Rotation
5.0L Alpha and Bravo ZC
LH
5.0LX Alpha ZD
LH
5.7L Bravo MJ
LH
5.7L Alpha
MJ
MB
LH
5.7L Bravo
CD
MD
LH
5.7L Alpha EFI
CD
MD
LH
5.7L Bravo EFI
MD
MJ
LH
5.7LX, Alpha
5.7LX Bravo
350 Magnum Alpha
5.7L EFI/MP Bravo
CD
MD
350 Magnum EFI
Alpha Gen +
MH
350 Bravo EFI MH
350 Magnum MPI Gen +
Bravo and Blackhawk
MIE (Inboard) Code Rotation
5.7L
MM
NN
LH
NR
RH
5 7L C titi Ski
MB
RH
5.7L Competition Ski
MJ
MB
LH
350 Magnum Tournament Ski
MH
CD
MD
LH
350 Magnum EFI
Tournament Ski
350 Magnum EFI/MP
Tournament Ski
CD
MD
LH
350 Magnum MPI Tournament
Ski (Black Scorpion)
MH