Mercury Mercruiser Marine Engine Number 23, GM V-8 454 CID (7.4L)/502 CID (8.2L) service manual (P/N 90-861326--1)

• Original OEM publication (Technical Code / Part No. 90-861326--1, Edition March 1999) straight from the manufacturer.
• 1,027 pages (Book 1 of 2) packed with original manufacturer specifications, reference data, and exploded views.
• Covers various V8 sterndrive and inboard variants of the Gen. VI and L-29 series, including the 454 Mag MPI and 502 Mag MPI.
• Delco EST ignition systems, MEFI 1, 2, and 3 ECMs, Walter RV-36 V-Drives, Bravo and Blackhawk drives, water separating fuel filters.
• Comprehensive engine final alignment, closed cooling pressure tests, shift cable installation setups, scan tool data values, thermostat opening specifications, serpentine belt tensioning.

Marine System Coverage

This documentation breaks down the core systems of GM V8 marine engines. It provides exact service and maintenance data, including specific intervals for standard and Horizon models. You will find detailed technical breakdowns of drive components, engine removal procedures, and inboard transmissions like the Velvet Drive, Hurth, and the Walter V-Drive. Save yourself an expensive trip to the marine mechanic with professional step-by-step guides covering critical tasks such as precise shift cable installation and adjustment to prevent clutch failure, manual clearing of diagnostic trouble codes, and accurate engine alignment. The manual dives deep into complex electronic fuel injection (MPI and EFI) setups. It also covers both closed freshwater cooling and conventional seawater systems, exhaust configurations, and hydraulic power steering.

Diagnostics & MEFI Diagnostics

Need to trace a fault? The electrical wiring diagrams, fuel system flow diagrams, closed cooling system water flow diagrams, and highly detailed distributor assembly exploded views give you the foundation to understand the entire onboard setup. Stop relying on guesswork to figure out what triggered your malfunction indicator lamp. This PDF manual equips your workshop with the exact troubleshooting charts, sensor pinouts, and scan tool data needed to isolate electrical faults quickly without blindly swapping components.

When diagnosing these specific powerplants, do not mistake high oil consumption for piston ring failure; the 454 and 502 Mag MPI models utilize forged aluminum pistons that naturally consume up to one quart of oil every 15 hours under heavy loads due to required thermal clearances. Furthermore, when servicing the drivetrain, be highly precise with your remote control linkages—even slight misadjustments can cause the transmission to slip and will completely jeopardize the Velvet Drive warranty. Because fuel and ignition systems pose severe explosion risks, always ventilate the engine compartment thoroughly and adhere to strict shop safety practices before disconnecting any lines or testing electrical circuits to prevent severe injury.

Specifications and Engine Characteristics

Verifying compatibility is crucial before beginning any repair. This text provides the extensive spec tables and operating data required by technically minded owners and marine mechanics. It lists precise machine characteristics, such as the exact 4.47 x 4.00-inch bore and stroke for the 8.2-liter engines. Propshaft horsepower figures are detailed across the board, ranging from 275 HP for strict SAV1 Lake Constance standards up to 415 HP. High-density reference values are packed into every section. You get exact tightening specs, like the 31 Nm (23 lb-ft) requirement for specific power steering hose fittings. Fluid capacities, detailed electrical reference values for all sensors, ignition timing specs, and essential connector pinouts are all clearly laid out. The publication even calls out specialty equipment, like the Quicksilver Alignment Tool (91-805475A1), to help you match the right documentation to your exact boat project.