MerCruiser GM V-8 305/350 CID (5.0L/5.7L) Marine Engine Service Manual No. 17 (P/N 90-823225-1)

MerCruiser Service Manual No. 17 (publication 90-823225--1) covers Sections 1 through 9 for GM V-8 5.0L (305 CID) and 5.7L (350 CID) marine engines, including the listed MCM Alpha, MCM Bravo, MIE Ski, and MIE Inboard configurations.

• Engine repair: Engine removal and alignment, cylinder-head reconditioning, valve-train service, bearing inspection, piston work, and timing-chain or timing-gear procedures.

• Carburetors and fuel delivery: MerCarb 2-barrel, Rochester 4-barrel, and Weber 4-barrel repair, mechanical fuel-pump testing, and fuel-filter service.

• EFI diagnosis: Throttle-body and multi-port injection troubleshooting, ECM fault-code checks, fuel-pressure relief, injector balance testing, and sensor replacement.

• Electrical systems: Thunderbolt IV and V ignition diagnosis, starter and alternator repair, instrumentation tests, and configuration-specific wiring diagrams.

• Cooling and exhaust: Seawater-pump output testing, closed-cooling pressure tests, heat-exchanger cleaning, and manifold, elbow, riser, and exhaust-shutter service.

• Driveline and steering: Inboard transmission service, Hurth overhaul, shift-cable adjustment, propeller-shaft checks, and power-steering pump service and bleeding.

Written for Mercury Marine dealers, mechanics, and service personnel, this manual assumes familiarity with the products, recommended service procedures, and required tools.

Model Coverage and Engine Identification

Match the model and serial range in the coverage list above before choosing procedures. On MCM Alpha models, OF601957 and above identifies the 5.7LX; the 5.7L EFI and 5.7LX EFI have separate starting points at OF286830 and OF752400.

Engine-code tables and cylinder-head identification distinguish Gen+ from earlier builds, flat from roller lifters, and standard from opposite rotation. That helps match parts and tune-up data to the engine before repair.

Engine Removal, Alignment, and Overhaul

Installation sections distinguish Alpha and Bravo packages with or without driveshaft extensions, plus Velvet Drive and Hurth inboard installations. They cover engine-to-gimbal-bearing alignment and identify Quicksilver alignment tool 91-805475A1.

The alignment cautions explain how forcing the tool or moving the engine with it engaged can damage the gimbal bearing or engine coupler. Internal engine procedures extend to valve-guide repair, crankshaft and connecting-rod bearings, camshaft inspection, and oil-pump service.

Transom assembly and sterndrive-unit repair require the appropriate separate Stern Drive Service Manual.

Observe the manual's lifting, battery-isolation, and engine-compartment ventilation precautions during engine removal and fuel or electrical work.

Carburetor and EFI Repair

Carburetor chapters cover disassembly, inspection, reassembly, float and choke settings, and idle-mixture adjustment. EFI coverage separates throttle-body injection from multi-port injection, with Vapor Separator Tank (VST) and Cool Fuel layouts, including Black Scorpion induction components.

Fault-code reading and clearing procedures cover both scan tools and a non-scan diagnostic code tool, including the listed Rinda 94008. Non-scan diagnosis still requires appropriate test equipment.

The ECM Connector and EFI Symptoms Charts identify J-1/J-2 circuits; the Engine Cranks but Will Not Run charts separate ignition and fuel checks. Injector balance testing compares fuel-pressure drops to help identify uneven injector delivery.

BOS/SAV emissions coverage adds ported-vacuum-switch and PCV checks, sealed idle-mixture-screw service, and the propane-assisted idle-setting procedure.

Ignition, Charging, and Wiring

Starting, ignition, charging, and instrumentation have separate sections. Starter coverage includes direct-drive and PG200, PG250, and PG260 units; charging-system repair covers Mando alternators.

Thunderbolt IV and V procedures address base timing, with Thunderbolt V idle adjustments and knock-control testing. The Thunderbolt V Spark Control Graph explains advance functions, while EFI harness diagrams distinguish VST from Cool Fuel wiring and show changes to lanyard-stop and dual-engine data-link connections.

Cooling Systems and Exhaust

The Water Flow Diagrams distinguish seawater-cooled systems from closed systems with coolant or raw-water flow through the exhaust manifolds. Procedures cover thermostat testing, heat-exchanger and pressure-cap checks, cylinder-head-gasket leak testing, and heat-exchanger/fluid-cooler cleaning.

Exhaust coverage includes manifold and elbow inspection, riser installation, exhaust-flapper/water-shutter replacement, and Silent Choice troubleshooting. Alpha drive-mounted seawater-pump repairs are referred to the separate sterndrive manual.

Inboard Transmissions and Power Steering

Velvet Drive in-line and V-drive coverage includes removal, installation, shift-cable adjustment, pump indexing, and pressure testing; internal overhaul is referred to Velvet Drive literature. Walter V-Drive arrangements are also covered.

The Hurth 630A down-angle transmission section goes further into disassembly, clutch and bearing work, reassembly, and functional testing. Driveshaft, bearing-support, and propeller-shaft inspection procedures follow.

Power-steering coverage includes hydraulic hoses, fluid coolers, pulley replacement, bleeding, and a System Flow Diagram. The pulley-service warning specifies Kent-Moore J-25034 and explains why a tapered puller can damage the pump shaft.

Tune-Up Specifications and Fluid Capacities

Maintenance schedules accompany tune-up tables with model-specific idle and W.O.T. ranges, LH/RH firing orders, spark-plug gaps, base timing, and thermostat specifications. Engine repair data includes bore/stroke dimensions, compression checks, oil and fuel pressures, torque sequences, clearances, wear limits, and electrical test values.

Fluid-capacity tables distinguish MCM from MIE installations and the different cooling and transmission arrangements. Seawater-system capacities are identified for winterization use.

PDF Navigation and Diagram Readability

Service text is searchable, but some wiring labels are graphics and cannot be found by text search. PDF bookmarks are only partly reliable: some links are inactive or misdirected, and some section labels are incorrect. Small wiring labels require zooming for comfortable reading.

This printable 967-page PDF combines Sections 1–4 (426 pages) and Sections 5–9 (541 pages). Those totals include the cover, five preliminary pages, and 44 intentionally blank pages.