OMC Sterndrive 90, 120, 150, 2.5L, 3.0L, 4.3L V6, 5.0L V8, 5.7L V8, 7.5L V8 Service Manual 1964–1986 (P/N 3400)

This 572-page PDF is the Seloc OMC Stern Drive 1964-86 aftermarket repair manual, identified by Seloc as Stock No. 3400. It is not an OMC factory service publication. The manual follows the original OMC drive families and their matched gasoline engines across the 1964-1986 model years, separating procedures where shift design, lower-unit construction, or engine family changes. Its depth is best suited to experienced marine mechanics and advanced owners who have suitable lifting, pressing, measuring, and electrical test equipment.

• Drive-generation coverage separates 1964-77 Electromatic units, the 1978-81 mechanically assisted power-shift/prop-exhaust design, and the 1982-86 mechanical-linkage units, with model-specific differences for early Type 1, Type 2, and Type 3 lower units and later 400/800 drives.
• For upper and lower gear cases, the manual details stern drive removal and installation, ball-gear and bearing-housing work, worm-gear steering, water-pump service, lower-unit disassembly, propeller-shaft service, oil-pump and forward-gear work, pinion-bearing shimming, and final shift adjustment.
• Engine chapters cover removal and installation, oil pumps and manifolds, cylinder-head reconditioning, piston-and-rod service, camshafts, crankshafts, main bearings, rear seals, timing chains, valve-lash or lifter-clearance checks, and mechanical troubleshooting for the covered GM-based and Ford engines.
• Fuel, ignition, and electrical work spans single- and dual-diaphragm fuel pumps; Rochester BC, RBS, 2GC, and 4MV plus Holley carburetors; Delco-Remy, Mallory, Autolite, and Prestolite distributor service; charging-system diagnosis; starter overhaul and bench testing; gauges, warning lights, and dual-battery installations.
• SelecTrim, hydraulic pump and motor, manual-release valve, Tru-Course steering, mechanical steering, over-under helm, shift boxes, throttle cables, tilt motor, hammer-blow coupling, and tilt clutch/worm gear all receive dedicated repair, adjustment, and test coverage.
• Reference sections provide tune-up and carburetor tables, spark-advance charts, engine specifications, torque tables, gear ratios, oil capacities, electrical test data, model-specific wire identification, system troubleshooting, sectional drawings, and exploded assembly views.

Drive and Engine Identification

The early-drive section explains that Type 1 was the small lower unit used on 88-90 hp and some 120 hp applications. Type 2 was the larger 1964-67 design without drivetrain shims, while Type 3 was the shimmed 1967-77 version. For the later family, 120 and 140 hp installations are identified as 400 drives and larger-power applications as 800 drives; after 1981, OMC generally used engine displacement instead of the 400/800 series designation. These distinctions matter when selecting a gear case, shim gauge, bearing tool, or overhaul procedure.

Engine coverage is equally specific. It includes 153/181 CID four-cylinder and 250 CID inline-six engines; Buick/Kaiser/GM 225, 229, and 262 CID V6 applications; GM V8 families including the later 5.0 and 5.7 Liter versions and older big-block applications; and Ford 302/351 CID V8 engines. In practical terms, the later metric designations are 2.5/3.0 Liter four-cylinder, 3.8/4.3 Liter V6, and 5.0/5.7 Liter V8 configurations. Although coverage reaches 1986, this manual does not contain Cobra, King Cobra, or SX drive procedures.

400/800 Drive Work and Tooling

The later lower-unit material goes well beyond routine service. It covers the shift converter and cable, power-assist servo, propeller shaft and shifter, driveshaft bearing housing, pinion-bearing race, oil pump and forward gear, shift-cable indexing, and operational adjustment. OMC tools are identified where the repair depends on controlled bearing position or preload, including shim gauge 314725, bearing-cup tools 314434/314436, press and holding tools 314437/314438, drive gauges 908573/909078, and 400/800 pinion gauges 315767/321520.

Illustration coverage includes a detailed OMC stern-drive section view, a 400/800 Series section view, an exploded 1967-77 drive, an exploded 400/800 lower unit, the OMC instrument-and-switch wiring diagram, and functional tilt, trim, and ignition circuit diagrams for the applicable engine groups.

Manual-Specific Repair Cautions

The water-pump section warns that replacing the pump without inspecting the swivel housing, pickup tube, and related seals can allow exhaust leakage to compromise the new pump and engine cooling. Gearcase repair also depends on correct, model-specific shimming and seal orientation; distorted or mismatched shims can upset bearing preload and gear mesh, leading to rapid gear or bearing damage.

The final chapters add intermediate-housing boot and ball-gear driveshaft service, fiberglass and below-waterline care, off-season storage, and pre-season preparation. Because the procedures include engine lifting, powered shift checks, fuel-system repair, and hydraulic/electrical work, use appropriate marine shop equipment and follow the manual's safety precautions.