Mercury 2 HP, 3.5 HP, 3.6 HP, 4 HP, 4.5 HP, 6 HP, 7.5 HP, 9.8 HP, 9.9 HP, 15 HP, 18 HP, 20 HP, 25 HP, 35 HP, 40 HP Outboard Engines 1965–1990 Repair Manual (P/N 1404)

Seloc repair manual P/N 1404 for Mercury 2.2–40 HP, one- and two-cylinder, two-stroke outboards. The main coverage is 1965–1989, with selected timing and wiring entries extending to the Model 3.0 for 1990 and later. This is a Seloc publication rather than a Mercury OEM factory manual.

PDF Bookmarks and Wiring Diagram Detail

Search, navigation, and small labels: PDF text search is not available. Fifteen embedded bookmarks provide access to the contents, chapters, appendix, and wiring diagrams. Small wire-color labels and connector markings in the checked diagrams are readable when enlarged; dense diagrams require zooming.

One printable PDF with 520 pages, including five contents pages, 464 chapter pages, and 51 appendix pages. The appendix includes the wiring diagrams.

Outboard Tune-Up, Diagnosis, and Overhaul

The following is a selection of the manual’s contents. Additional topics include propeller selection and fiberglass-hull care.

• Maintenance and tune-up: Compression checks, spark-plug evaluation, submerged-engine service, water-pump checks, corrosion control, seasonal storage, and on-boat performance testing.

• Carburetors and fuel delivery: Eight A–H carburetor sections with step-by-step removal, disassembly, inspection, float and needle setup, reassembly, installation, and operating adjustments.

• Ignition and electrical diagnosis: Timing and synchronization procedures, stator and coil tests, charging-circuit checks, starter-solenoid troubleshooting, and large and small cranking-motor service.

• Powerhead repair: Teardown, crankshaft and end-cap bearing service, connecting-rod and piston inspection, cylinder honing, block inspection, reassembly, and installation.

• Gearcase and cooling service: Propeller removal, gearcase disassembly, bearing and seal replacement, backlash adjustment, water-pump repair, assembly, and installation.

• Hydraulic trim/tilt: Bleeding procedures, electrical and hydraulic fault isolation, component testing, cylinder service, pump repair, and electric-motor service.

• Controls and rewind starters: Commander shift-box overhaul and cable checks, plus separate disassembly, inspection, reassembly, and installation procedures for eight hand-rewind starter layouts.

Suited to readers who understand two-stroke engine operation and can use the dial indicator, timing light, tachometer, and torque wrench required for the relevant procedures.

Match the Correct Mercury Configuration

Coverage is organized by model, configuration, and beginning serial number. The timing index identifies 4709592 as a Model 200 change point. Separate procedures distinguish the 402, 35/40, 7.5/9.8, 18/25 and XD versions, 2.2/3.0, 4.0/5.0, 90cc, and 210cc families.

Wiring diagrams distinguish manual and electric starting, alternator equipment, and installations with or without remote control. Only the one- and two-cylinder configurations shown in the tables are covered. Three- and four-cylinder, inline-six, and V6 engines require other publications, including some Mercury 40 HP configurations.

Carburetor Families and Fuel-System Limits

Fuel diagnosis addresses restricted lines, weak pumps, rough idle, surging, and excessive consumption. Individual repair sections distinguish side-bowl and back-drag carburetors, center-round-bowl designs, rectangular- and round-bowl Mikuni units, Tillotson BC, Walbro WMC, and the manual’s “Keikhin” integral-pump design.

The fuel-pump section explains pressure testing and diaphragm service, with configuration-specific limits. Pumps on Models 3.5, 3.6, and 4.0 are described as replacement units rather than internally serviceable pumps; the pressure-check procedure also excludes integral-pump carburetors.

Auto Blend: Coverage includes oil-delivery operation, warning-horn diagnosis, storage preparation, and return-to-service checks. The manual treats Auto Blend as equipment supplied with appropriately equipped engines and advises against retrofitting it to other units.

Four Ignition Systems and Electrical Testing

The ignition chapters distinguish the Phelon flywheel magneto, Thunderbolt Phase Maker with points, Thunderbolt pointless capacitor discharge, and Thunderbolt capacitor discharge with one coil per cylinder. Polarity checks, spark testing, flywheel service, and model-specific test charts accompany those sections.

Electrical coverage extends to batteries, charging stators, solenoids, and cranking-motor components. The appendix explains the limits of resistance testing and identifies the Quicksilver Multimeter/DVA Tester 91-99750 for further ignition-coil checks.

Powerhead Layouts and Reed Access

Three repair sections distinguish Type A split blocks with an internal reed box, Type B split blocks with an external reed block, and Type C blocks with a cylinder head and reeds beneath the crankshaft. That layout-based organization helps prevent the wrong teardown or assembly procedure from being applied to a similar-looking engine.

Reed access differs substantially: Types A and C require powerhead disassembly, while the external Type B reed block can be serviced without dismantling the powerhead.

The piston-service cautions explain how an incorrectly positioned ring can break during installation where locating pins are fitted. Models 6.0, 8.0, 9.9, 15, and 210cc use pistons without those locating pins.

Gearcase Types and Water-Pump Access

Type A gearcases have no reverse gear; Types B and C provide reverse, with Type C using a different shift arrangement. Type D places the water pump on the propeller shaft, allowing impeller replacement without a complete gearcase teardown.

Service-tool references include Mercury lockring tool 91-5252A1 and lower-unit puller 91-27780. Water-pump cautions explain why reversing a reused impeller can cause premature failure.

Trim Components, Commander Controls, and Starters

Trim/tilt troubleshooting separates electrical faults from hydraulic faults before component service. The control-valve and pump gear assemblies are identified as replacement assemblies when defective, rather than components for internal repair.

Commander coverage follows the shift box through inspection, assembly, cable checks, and installation. Hand-rewind starters are identified visually as Types A–H, with separate procedures for their different springs, pawls, sheaves, and interlocks.

Appendix Tables and Assembly Drawings

The appendix supplies engine and tune-up tables, carburetor jet/elevation data, piston and cylinder specifications, and reed-stop openings. Further tables cover gearcase oil capacities, gear data, backlash, stator and coil checks, and component-specific torque specifications.

Illustrations include the Phelon magneto schematic, Thunderbolt Phase Maker functional diagram, charging and cranking circuits, exploded powerhead and lower-unit assemblies, and hydraulic trim-pump and Commander-control views. Maintenance guidance also distinguishes freshwater and saltwater service requirements.

Gasoline, high-voltage ignition, rotating flywheels, loaded rewind springs, and supported trim components require the isolation and handling precautions described in the manual.

Gearcase Oil Capacity Examples

The lower-unit chart specifies 5.50 fl oz for Model 18 configurations from 1981–1983 and 7.60 fl oz for the 18XD from 1984–1985. These separate model-specific capacities appear alongside gear tooth counts and ratios, with the matching gearcase types identified in the following appendix table.