Mercury MerCruiser Marine Engine GM V-8 (305, 350, 377 CID) 1998–2001 Service Manual No 24 (P/N 90-861327--1)

The supplement is intended for use with Manual #24, identifying specifications, components, and repair procedures that differ from the 5.7L/350 CID engine. Together, the two publications provide shared GM V-8 service material and the engine-specific information needed for the 6.2L builds.

Scope limits: Sterndrive-unit removal and internal sterndrive repair require the applicable Sterndrive Service Manual. Internal Velvet Drive transmission repair requires separate Velvet Drive service literature; power-steering pump repair is referred to the appropriate sterndrive manual.

Searchable PDFs, Bookmarks and Page Count

Search and diagram detail: Both PDFs support text search and have section bookmarks. The base manual’s “Models Covered” bookmark points to an external file not included in the ZIP. Small wiring labels require zooming for detailed reading.

ZIP download containing two printable English-language PDFs, totaling 1,106 pages. The base manual includes 18 cover/preliminary pages, including one publication-label sheet, and 38 intentionally blank pages. The supplement includes 10 cover/preliminary pages, including one blank page, and five additional blank pages.

GM V-8 Engine Repair, Fuel Systems and Marine Installations

The following selected coverage highlights outline major workshop tasks. Other included topics range from used-spark-plug analysis to Silent Choice exhaust-system troubleshooting.

• Engine mechanical repair: MCM/MIE removal, installation, and alignment; cylinder-head and valve work; piston, connecting-rod, crankshaft, timing-chain, camshaft, and oil-pump service.

• Fuel-system service: Mercarb two-barrel carburetor repair, Cool Fuel delivery, throttle-body EFI, multi-port injection, fuel-pressure testing, and injector balance testing.

• Ignition and charging: Thunderbolt V and EFI/MPI ignition, starter testing and repair, alternator diagnosis, Mando alternator overhaul, and instrumentation checks.

• ECM diagnostics: MEFI 1/2/3 trouble-code charts, scan-tool data, symptom-based fault isolation, connector-pin references, and model-specific wiring diagrams.

• Cooling and exhaust: Seawater and closed-cooling systems, heat-exchanger tests, seawater-pump service, thermostat testing, and exhaust manifold, elbow, riser, and collector work.

• Transmissions and shafts: Velvet Drive and ZF (Hurth) identification, adjustment, fluid service, removal/installation, pressure testing, and drive-shaft/propeller-shaft checks.

• Scheduled maintenance and storage: Installation-specific maintenance schedules, power-steering bleeding, belt inspection and adjustment, flushing, winterization, power-package layup, and recommissioning.

Written for dealer mechanics and company service personnel already familiar with MerCruiser service procedures and trained in common hand tools and specified service equipment.

Internal Engine Work and Alignment

Internal-engine sections provide step-by-step procedures for valve-guide and valve-seat repair, valve-spring testing, rocker-arm stud replacement, rear-main-seal service, camshaft-bearing installation, and oil-pump disassembly and reassembly.

Inspection tables cover bearing clearances, cylinder and piston dimensions, camshaft and valve-train data, lubrication, approved sealants, and component-specific torque specifications. Listed Kent-Moore equipment includes the J6098-01 camshaft-bearing installer/remover and J26817-A rear-main-seal installer.

The MCM installation section warns that substitute alignment tools can damage the gimbal bearing or engine coupler; it specifies Quicksilver 91-805475A1 or the properly modified 91-57797A3.

Injection Hardware and Fault Isolation

6.2L component differences: The injection sections distinguish MX 6.2 MPI hardware from the Black Scorpion plenum and fuel-rail arrangement. Component procedures cover the throttle body, TP and MAP sensors, IAC valve, knock sensor and module, ECT sensor, fuel injectors, relays, and ECM.

Diagnostic references: Scan-tool normal-data tables and ECM J-1/J-2 circuit charts connect operating readings and wiring faults with possible symptoms. Hard-start, rough-idle, and lack-of-power charts support fault isolation before individual components are selected for testing.

Named equipment includes the Quicksilver Digital Diagnostic Terminal 91-823686A2, Fuel Pressure Gauge Kit 91-16850A5, and EFI Timing Tool 91-805747A2.

Starting/charging harness drawings distinguish MCM MX 6.2 MPI from MIE/Black Scorpion installations. Further references include the 6.2 fuel/ignition harness, MEFI wiring-system schematics, ECM connector views, and seawater/closed-cooling flow diagrams, with Mercury and GM EST distributor configurations identified where applicable.

Cooling, Charging and Driveline Details

Maintenance planning: Tables separate sterndrive and inboard use, including salt/brackish/polluted-water flushing requirements. Fluid-capacity and approved-fluid tables distinguish engine, sterndrive, Velvet Drive, and ZF (Hurth) applications.

Alternator repair limits: The charging chapter includes Mando alternator disassembly and reassembly. The Delco Remy alternator described in the same chapter is replaced as an assembly rather than internally repaired.

Transmission rotation: The Hurth section specifies left-hand-rotation engines; pairing one of these transmissions with a right-hand-rotation engine can cause severe transmission damage.

Fuel and ignition service must follow the manual’s battery-isolation, fuel-pressure-relief, leak-check, and ventilation precautions because gasoline vapors and electrical sparks create a fire or explosion hazard.

Examples of 6.2L Camshaft and Flywheel Inspection Limits

For the 377 CID engine, the supplement’s camshaft inspection specifications give a maximum runout of 0.0026 in. The flywheel specification lists a maximum runout of 0.008 in. These limits accompany the component inspection and replacement information in the engine section.