Name: Mercury MerCruiser MCM 7.4L MPI
Brand: Mercury
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GENERAL SYSTEM DIAGNOSTICS

SERVICE MANUAL NUMBER 23

90-861326--1 MARCH 1999 Page 5E-21

a-IC Module

b-To Drawing 4 Of 4

c-Harness Connector

d-Ignition Coil

e-ECM Ground

f-ECM Ground

g-Ignition Control Signal

h-Ignition Control Reference High

i-Ignition Control Bypass

j-Ignition Control Reference Low

k-Coolant Over Temperature

l-Discrete Switch

m-Discrete Switch

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Index

Important Information 18
- Table of Contents8
- Introduction9
- How to Use this Manual9
  - Page Numbering9
- How to Read a Parts Manual10
- Directional References11
- Engine Rotation11
- Engine Serial Number Locations12
- Propeller Information13
- Water Testing New Engines13
- Boat and Engine Performance14
Important Information 118
- Lubricants / Sealants / Adhesives19
- Maintenance Schedules20
  - Maintenance Intervals20
  - Scheduled Maintenance that Can be Performed by Owner/Operator20
  - Scheduled Maintenance that Should be Done by Dealer21
  - Scheduled Maintenance that Should be Done by Dealer22
  - Scheduled Maintenance that Can be Performed by an Owner/Operator23
  - Scheduled Maintenance that Should be Done by Dealer23
- Firing Order28
- Fluid Capacities28
  - Engines28
  - Transmissions29
  - Sterndrive Units29
- 20-Hour Break-In Period29
- After Break-In Period30
- End of First Season Checkup30
- Specifications31
  - Fuel Recommendations31
  - Test for Alcohol Content in Gasoline32
- Power Steering Fluid32
- Transmission Fluid32
- Coolant for Closed Cooling System33
- Crankcase Oil33
  - Overfilled Crankcase34
  - Checking Engine Oil Level/Filling34
- Changing Oil and Filter35
- Changing Water Separating Fuel Filter36
  - MCM (Sterndrive) Models36
  - MIE (Inboard) Models37
- Power Steering System38
  - Checking Fluid Level38
  - Filling and Bleeding39
- Closed Cooling System40
  - Checking Coolant Level40
  - Flushing System MCM (Sterndrive)41
  - Flushing System MIE (Inboard) - Except 454 Mag MPI Horizon43
  - Flushing System MIE (Inboard) 454 Mag MPI Horizon45
- Transmission Fluid49
  - Checking Fluid Level49
- Lubrication50
  - Throttle Cable50
  - Shift Cable51
  - Shift Cable and Transmission Linkage . 1B-3451
  - Engine Coupler / U-Joint Shaft Splines52
  - Drive Shaft Extension Models53
  - Starter Motor54
- Cleaning Flame Arrestor55
  - Plastic Side Mounted Flame Arrestor . 1B-3855
  - Plastic Front Mounted Flame Arrestor 1B-3956
  - Metal Side Mounted Flame Arrestor56
- Serpentine Drive Belt57
  - Component Location57
  - Inspecting59
  - Replacing And/Or Adjusting Tension59
- Ignition Timing60
- Cold Weather or Extended Storage61
  - Precautions61
  - Power Package Layup62
Important Information 184
- Precautions85
- Used Spark Plug Analysis86
- Spark Plug Analysis87
  - Normal Condition87
  - Chipped Insulator87
  - Wet Fouling (Oil Deposits)87
  - Cold Fouling88
  - Overheating88
  - High Speed Glazing88
  - Scavenger Deposits89
  - Pre-Ignition Damage89
  - Reversed Coil Polarity89
  - Splashed Deposits90
  - Mechanical Damage90
- Poor Boat Performance And/Or Poor Maneuverability91
- Improper Full Throttle Engine RPM92
  - RPM too High92
  - RPM too Low92
- Engine Cranks over but will Not Start or Starts Hard93
  - Important Information93
  - Fuel System Rich93
  - Fuel System Lean93
  - Miscellaneous93
- Charging System Inoperative94
- Engine will Not Crank over94
- Instrumentation Malfunction95
- Noisy Alternator95
- Radio Noise95
- Engine Runs Poorly at Idle96
- Poor Fuel Economy96
- Engine Acceleration Is Poor97
- Engine Runs Poorly at High RPM97
- Engine Noise98
  - Important Information98
  - Valve Cover Area99
  - Cylinder Area99
  - Camshaft Area100
  - Crankshaft Area100
  - Miscellaneous101
- Troubleshooting with Vacuum Gauge98
- Oil Pressure102
  - Miscellaneous102
  - Low Oil Pressure103
  - High Oil Pressure103
- Excessive Oil Consumption104
- Water in Engine105
  - Important Information105
  - Water on Top of Pistons106
  - Water in Crankcase Oil106
- Engine Overheats107
  - Mechanical107
- Engine Overheats108
  - Cooling System108
  - Insufficient Water Flow from Belt Driven Seawater Pickup Pump109
- Power Steering110
  - Poor, Erratic or no Assist110
  - Noisy Pump111
  - Fluid Leaks111
Removal and Installation 2113
- Lubricants / Sealants / Adhesives114
- Tools114
- Torque Specifications114
- Preparation115
- Removal115
- Installation116
Removal and Installation 2155
- Preparation157
- Removal157
- Installation158
  - Engine Installation and Initial Alignment158
  - Engine Final Alignment160
- Engine Connections163
- Seawater Hose Connection163
- Electrical Connections164
- Fuel Supply Connections164
- Exhaust Hose Connection165
- Throttle Cable Installation and Adjustment165
- Shift Cable Installation and Adjustment171
- Velvet Drive Transmissions171
Removal and Installation 2181
- Torque Specifications182
- Preparation183
- Removal183
- Installation184
  - Engine Installation and Initial Alignment184
  - Engine Final Alignment187
- Engine Connections191
- Shift Cable Installation and Adjustment199
Engine205
- Mag / 502 Mag / 8.2L211
- General Information220
  - Engine Identification220
  - Cylinder Head Identification221
  - Engine Rotation221
  - Crankshaft222
  - Piston and Connecting Rods222
  - Camshaft and Drive222
  - Cylinder Head222
  - Valve Train222
  - Lubrication System222
- Bearing Failures224
- Piston Failures226
  - Pre-Ignition226
  - Detonation227
- Engine Mounts229
- Rocker Arm Cover232
  - Removal232
  - Installation232
- Intake Manifold233
  - Removal233
  - Cleaning and Inspection233
  - Installation234
- Rocker Arm/Push Rod236
  - Removal236
  - Cleaning and Inspection236
  - Installation236
  - Rocker Arm Stud Kit237
- Hydraulic Roller Valve Lifters237
  - Locating Noisy Lifters238
  - Removal239
  - Installation239
- Valve Adjustment237
- Valve Stem Oil Seal / Valve Spring240
  - Removal - Head Installed240
  - Valve Assembly (Exploded View)241
  - Valve Installation - Head Installed242
- Cylinder Head243
  - Removal243
  - Cleaning243
  - Inspection243
- Cylinder Head and Valve Conditioning245
  - Disassembly245
  - Cleaning245
  - Inspection246
  - Valve Guide Bore Repair247
  - Valve Springs - Checking Tension248
  - Valve Seat Repair248
  - Valve Grinding249
  - Reassembly250
- Crankcase Oil Dipstick Specifications252
  - All Engines252
- Oil Pan253
  - Removal253
  - Installation253
- Oil Pump255
  - Removal255
  - Disassembly256
  - Cleaning256
  - Reassembly256
  - Installation257
- Torsional Damper257
  - Removal257
  - Installation258
- Front Cover / Oil Seal259
  - Oil Seal Replacement (Without Removing Front Cover)259
- Front Cover260
  - Removal260
  - Cleaning260
  - Inspection260
  - Installation260
- Flywheel262
  - Removal262
  - Inspection263
  - Installation263
- Rear Main Oil Seal264
  - Removal264
  - Cleaning and Inspection264
  - Installation265
- Main Bearings265
  - Inspection265
  - Checking Clearances265
  - Replacement267
- Connecting Rod Bearings269
  - Inspection and Replacement269
- Connecting Rod / Piston Assembly271
  - Removal271
- Crankshaft278
  - Removal278
  - Cleaning and Inspection278
- Timing Chain and Sprocket280
  - Removal280
  - Cleaning and Inspection280
  - Installation280
- Crankshaft Sprocket281
  - Removal281
  - Installation281
  - Checking Timing Chain Deflection281
- Camshaft282
  - Measuring Lobe Lift282
  - Removal282
  - Inspection283
  - Installation283
- Camshaft Bearings283
  - Removal283
  - Inspection284
  - Installation284
- Cylinder Block285
  - Cleaning285
  - Inspection285
- Compression Test 3A-85289
- Oil Filter By-Pass Valve and Adaptor 3A-86290
  - Inspection and / or Replacement 3A-86290
Electrical Systems292
- Starting System Components293
- Direct Drive Starter Motor294
  - Identification294
  - Electrical Circuit Description294
- Lubricants / Sealants / Adhesives295
- Specifications295
- Direct Drive Starter Motor Exploded View 4A-6297
- Delco PG260 Starter Motor307
  - Identification307
  - Electrical Circuit Description307
- Specifications308
- Lubricants / Sealants / Adhesives309
- PG 260 Starter Motor Exploded View310
- PG 260 Starter Motor Repair311
- PG260F1 Starter Motor325
- Starter Motor Repair328
- Mando Starter Motor339
  - Identification339
  - Electrical Circuit Description339
- Description341
  - Exploded View341
Electrical System342
- Lubricants / Sealants / Adhesives343
- Specifications343
- Torque Specifications343
- Ignition Control System Components344
- Ignition Timing354
  - Checking/Adjusting354
Electrical System356
- Description357
  - Multiple EFI Engine Battery Precautions361
- Mando 65 Amp Alternator357
  - Identification357
- Replacement Parts Warning357
- Specifications357
- EFI Electrical System Precautions361
- Drive Belt Tension Adjustment362
- Periodic Maintenance362
- System Components362
- Troubleshooting Tests363
- Exploded View369
- Alternator Repair370
- Installation383
  - Battery Isolator Diagram384
Electrical System390
- Identification391
- Special Information392
  - Lighting Options392
- Gauges394
- Senders398
- Switches404
- Audio Warning System406
Electrical System412
- Wiring Colors for Mercruiser413
- Starting and Charging System Wiring Harness Diagrams415
- Fuel Injection Wiring Harness Diagrams423
- MEFI 2 MIE 7.4L MPI Model425
- MEFI 3 MCM 7.4L MPI Bravo and MIE 7.4L Inboard428
- Instrumentation Harness Diagrams429
- MCM (Sterndrive)429
- MIE (Inboard)430
- Dual Station Wiring431
Fuel System438
- Lubricants / Sealants / Adhesives439
- Specifications439
- Tools439
- Torque Specifications439
- Fuel Supply Connections440
- Precautions440
- Replacement Parts Warning440
- Fuel Delivery System441
  - Recommendations441
- Special Tools443
  - Rinda Technologies Special Tools444
- Cool Fuel System Exploded View445
- Fuel System Flow Diagram447
- Water Separating Fuel Filter448
- Cool Fuel System Repair449
- Vacuum Line Routing457
Fuel System460
- Identification461
  - Electronic Control Module (ECM)461
- General Information462
- Abbreviations465
- ECM Self-Diagnostics466
- Special Tools471
- Precautions472
- Electronic Control Module (ECM) and Sensors474
- Spark Management486
- Fuel Metering System492
Fuel System502
- Precautions503
- Exploded Views504
- 454 / 502 Mag MPI Multi-Port Components509
- Fuel Pressure Relief Procedure509
- 454 / 502 MPI and 8.2L MPI - Sensor and Module Servicing523
- Vacuum Line Routing536
  - 502 MPI and 8.2L MPI Models 5C-35536
- Exploded View537
  - 7.4L MPI Intake Manifold, Plenum and Fuel Rail537
  - 7.4L MPI Throttle Body and Adapter Components539
- 7.4L MPI Components540
- Fuel Pressure Relief Procedure540
- Vacuum Line Routing557
  - 7.4L MPI Models557
Fuel System560
- Diagnostic Trouble Codes for the MEFI 1 454 / 502 Mag MPI and 8.2L MPI Engines561
  - MEFI 2 7.4L MPI Engines561
  - (8.2L) Engines561
- Troubleshooting561
- Scan Tool Normal Specifications564
  - Neutral)564
- Important Preliminary Checks565
- Visual/Physical Check565
- Hard Start Symptom567
- Surges And/Or Chuggles Symptom570
- Lack of Power, Sluggish or Spongy Symptom572
- Detonation/Spark Knock Symptom575
- Hesitation, Sag, Stumble Symptom578
- Cuts Out, Misses Symptom580
- Rough, Unstable, or Incorrect Idle, Stalling Symptom582
- Poor Fuel Economy Symptom586
- Backfire Symptom589
Fuel System594
- Diagnostic Circuit Check595
  - Scan Tool Normal Specifications (Idle / Warm Engine / Closed Throttle / Neutral)595
- MEFI 1 - ECM Connector Chart for 454/502 Mag MPI and 8.2L MPI596
- Diagnostic Trouble Codes598
- Special Tools600
- MEFI 1 - 454/502 Mag MPI and 8.2L MPI Symptom Chart (J-1 Circuits)604
- MEFI 1 - 454/502 Mag MPI and 8.2L MPI Symptom Chart (J-2 Circuits)606
- MEFI 2 - ECM Connector Chart for 7.4L MPI616
- MEFI 2 - 7.4L MPI Symptom Chart (J-1 Circuits)619
- MEFI 3 - ECM Connector Chart633
- Test Example643
- General Diagnostic Tests644
Fuel System746
- Clearing Trouble Codes748
  - Clearing Codes Using Diagnostic Code Tool (Non-Scan)748
  - Clearing Codes Using Scan Tool (Scan)748
- Diagnostic Testing Without a Scan Tool749
  - Voltage Low756
  - Temperature Indicated759
- Code 41 (1 of 3): Ignition Control (IC)770
  - Open Bypass Circuit, or Grounded773
  - Bypass Circuit773
- Code 44 (1 of 3): Knock Sensor (KS)778
  - Code 51 (1 of 2): Calibration Memory Failure (Non-Scan)781
- Diagnostic Testing Using a Scan Tool783
  - Temperature Indicated783
- Code 15 (1 of 3): Engine Coolant785
- Code 21 (1 of 2): Throttle Position (TP) Sensor Circuit (Scan) High Signal Voltage788
- Code 51 (1 of 1): Calibration Memory Failure (Scan)813
- Code 52 (1 of 1): EEPROM Failure (Scan)814
Cooling System826
- Tools827
  - Special Tools827
- Torque Specifications827
- Lubricants / Sealants / Adhesives828
- Specifications828
  - Cooling System Capacity828
  - Thermostat828
- Seawater Inlet Recommendations829
- Seawater Pickups830
  - Through-Hull Mounted830
- Sea Strainer833
  - Removal833
  - Installation834
- Seawater Pickup Pump835
  - Seawater Pump Disassembly836
  - Seawater Pump Reassembly837
- Seawater Pump Bearing Housing838
- Water Circulating Pump844
- Drive Belt Tension Adjustment845
- Flushing Seawater Cooling System846
  - 454/502 Mag MPI and 8.2L MPI846
  - 454 Mag MPI Horizon Models847
- Seawater Strainer848
- Thermostat849
- Auxiliary Hot Water Heater Installation852
- Water Flow Diagram853
- Water Tap Locations for Propshaft Coolers853
Cooling System856
- Cooling856
- Lubricants / Sealants / Adhesives857
- Specifications857
- Torque Specifications857
- Description858
- Maintaining Coolant Level858
- Pressure Cap Maintenance859
- Heat Exchanger Repair860
- Seawater Pickup Pump Maintenance860
- Testing Closed Cooling System860
- Thermostat865
- Changing Coolant868
- Cleaning System869
  - Closed Cooling Section869
  - Seawater Section870
- Filling Closed Cooling Section871
- Auxiliary Hot Water Heater Installation873
- Heat Exchanger Bracket Hardware874
- Heat Exchanger Hose Connections875
- Closed Cooling System Water Flow Diagram876
  - MCM / MIE Models876
- (Coolant Section of System)877
Exhaust System880
- Exhaust System Requirements881
- Exhaust Tube Requirements883
Exhaust System886
- Lubricants / Sealants / Adhesives887
- Removal887
- Torque Specifications887
- Cleaning888
- Inspection888
- Installation889
Exhaust System891
- Description892
- Preparation892
- Sealants892
- Torque Specifications892
- Exhaust Risers893
- Cast Iron Elbows with 3 Inch Riser895
- Installation Diagrams895
- Maintenance Instructions895
- Cast Iron Elbows with 3 Inch Riser and Muffler Spacer896
- Cast Iron Elbows with 6 Inch Riser897
- Cast Iron Elbows with 6 Inch Riser and Mufflers898
Exhaust System900
- Lubricants/Sealants/Adhesives901
- Torque Specifications901
- Shutter Replacement902
- Component Replacement903
- Through-Transom Exhaust904
  - Shutter Replacement904
  - Component Replacement905
- Below Swim Platform Exhaust Pipe905
- Silent Choice Exhaust System906
- Exhaust Tube Installation907
- Air Tube Routing909
- Maintenance910
- Exhaust Muffler Kit911
- Cleaning and Inspection912
- Installation913
- Maintenance Instructions913
Drives916
- Velvet Drive In-Line (72C) Specifications917
- Important Information953
- Shift Cable Adjustment955
- Checking Transmission Fluid Level960
- Changing Transmission Fluid961
  - Draining Transmission961
  - Filling Transmission962
- Removal and Installation962
- Shift Lever Installation964
- Pressure Test965
- Transmission Repair965
Drives993
- Lubricants/Sealants994
- Tools994
- Flywheel Housing/Output Shaft Housing Repair (MCM Sterndrive Models)995
  - Disassembly995
  - Reassembly995
- Drive Shaft Repair (MCM Sterndrive Models)997
- Installation1000
- Bearing Support Repair (MCM Sterndrive Models)1002
- Propeller Shaft (MIE Inboard Models)1006
Power Steering1012
- Lubricants / Sealants1013
- Precautions1013
- Tools1013
- Power Steering Pump and Components (Exploded View)1014
- Belt Routing1015
- Serpentine Belt Adjustment1015
- Important Service Information1016
- Pump Pulley Replacement1016
- Checking Pump Fluid Level1017
  - Filling and Air Bleeding System1017
- Testing and Repair1017
- Pump Assembly1018

Mercury MerCruiser MCM 7.4L MPI User Manual

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Mercury MerCruiser MCM 7.4L MPI Specifications

Related product manuals

Brand	Mercury
Model	MerCruiser MCM 7.4L MPI
Category	Engine
Language	English