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

• Two-PDF factory set, 1,106 PDF pages total — Service Manual #24, P/N 90-861327--1 (October 1999), 895 pages; Supplement to Service Manual #24, P/N 90-861327000 (July 2000), 211 pages.
• Base-manual coverage includes GM V-8 MCM sterndrive engines in 305 CID (5.0L) and 350 CID (5.7L) carbureted, EFI, and 350 MAG MPI configurations, with Alpha and Bravo applications, plus MIE inboard and ski-engine material including the 5.7L Black Scorpion.
• The 377 CID supplement applies to MX 6.2 MPI MCM sterndrive and MIE inboard models, plus MX 6.2 Black Scorpion ski engines, serial number 0L680003 and above.
• Engine repair coverage reaches from MCM/MIE removal, installation, and alignment through cylinder-head and valve work, piston and connecting-rod service, crankshaft and bearing inspection, timing-chain work, camshaft service, oil-pump repair, and cylinder-block inspection.
• Fuel-system material spans the Mercarb two-barrel carburetor, Cool Fuel delivery system, throttle-body EFI, and multi-port injection, with fuel-pressure testing, injector balance testing, sensor and relay service, ECM diagnostics, trouble-code charts, and symptom-based fault isolation.
• Electrical support includes starter and alternator testing and repair, Thunderbolt V and EFI/MPI ignition, instrumentation checks, MEFI 1/2/3 circuits, connector-pin charts, and model-specific wiring diagrams.
• Maintenance and driveline sections address seawater and closed cooling, heat-exchanger and seawater-pump testing, exhaust manifolds and collectors, power-steering bleeding, Velvet Drive and ZF (Hurth) transmission service, shaft checks, seasonal storage, and recommissioning.

This factory service information was written and published by Mercury Marine’s Service Department. Mercury states that it was prepared for dealer mechanics and company service personnel already familiar with MerCruiser service procedures and trained in the use of common hand tools and specified service equipment.

Engine Mechanical and Maintenance

The 6.2L publication is a true supplement, not a stand-alone replacement for Manual #24. It identifies the specifications, components, and repair procedures that differ from the 5.7L/350 CID engine. Used as a set, the two PDFs provide both the shared GM V-8 service material and the engine-specific information needed for MX 6.2 MPI and MX 6.2 Black Scorpion builds.

Internal-engine sections include component-specific torque tables, dimensional inspection limits, bearing clearances, cylinder and piston specifications, camshaft and valve-train data, lubrication information, and approved sealants. Factory procedures cover valve-guide and valve-seat repair, valve-spring testing, rocker-arm stud replacement, rear-main-seal service, crankshaft and connecting-rod inspection, camshaft-bearing installation, timing-chain inspection, and oil-pump disassembly and reassembly. The listed equipment includes the J6098-01 camshaft-bearing installer/remover, J26817-A rear-main-seal installer, and other Kent-Moore engine tools.

Maintenance tables are separated by sterndrive and inboard use. They cover routine and scheduled service, salt/brackish/polluted-water flushing, engine and transmission fluids, belt inspection and adjustment, closed-cooling care, power-package layup, draining, and recommissioning. Capacity and approved-fluid tables distinguish the engine, sterndrive, Velvet Drive, and ZF (Hurth) applications.

Technical Specifications and Diagnostics

Tune-up data is organized by engine and installation type, with compression, oil- and fuel-pressure, ignition-timing, idle and wide-open-throttle, alternator, battery, spark-plug, and thermostat specifications. The 6.2L fuel-injection section separates MX 6.2 MPI hardware from the Black Scorpion plenum and fuel-rail arrangement, then covers the throttle body, TP and MAP sensors, IAC valve, knock sensor and module, ECT sensor, fuel injectors, relays, and ECM.

Diagnostic material includes scan-tool normal-data tables, diagnostic trouble-code identification, ECM J-1/J-2 circuit and symptom charts, and wiring-system schematics for Mercury and GM EST distributor configurations. Named tools include the Quicksilver Digital Diagnostic Terminal 91-823686A2, Fuel Pressure Gauge Kit 91-16850A5, and EFI Timing Tool 91-805747A2. Diagram coverage includes the MCM MX 6.2 MPI starting/charging harness, MIE and Black Scorpion starting/charging harness, 6.2 fuel/ignition harness, MEFI wiring-system diagrams, ECM connector views, and seawater/closed-cooling flow diagrams.

Scope Limits and Repair Cautions

Manual #24 covers engine removal and installation, but sterndrive-unit removal and internal sterndrive repair require the applicable Sterndrive Service Manual. Its Velvet Drive chapters provide identification, adjustment, fluid service, removal/installation, and pressure testing; internal transmission repair is referred to Velvet Drive service literature. Power-steering pump repair is likewise referred to the appropriate sterndrive manual.

The MCM installation section warns that substitutes for Quicksilver alignment tool 91-805475A1 or the properly modified 91-57797A3 can produce misalignment and damage the gimbal bearing or engine coupler. The Hurth section also 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.