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 Manual (PN 866375)

• 520-page PDF of Seloc manual 1404 for Mercury 2–40 HP, one- and two-cylinder, two-stroke outboards. The main coverage is 1965–1989, while the model-specific timing and wiring tables also list the 3.0 model for 1990 and later. This is a Seloc repair publication, not a Mercury OEM factory manual.
• Covers compression checks, spark-plug evaluation, fuel-pump testing, carburetor setup, water-pump inspection, submerged-engine service, lower-unit checks, ignition timing and synchronization, cranking and charging circuits, and final on-boat performance testing.
• Provides eight A–H carburetor sections with removal, disassembly, cleaning, inspection, float and needle setup, reassembly, installation, and operating adjustments for side-bowl, center-round-bowl, Mikuni, Tillotson BC, Walbro WMC, and the manual’s “Keikhin” integral-pump designs.
• Organizes powerhead repair by three block and reed layouts, then documents teardown, reed-block service, crankshaft and end-cap bearings, connecting rods, pistons, cylinder honing, block inspection, reassembly, and installation.
• Separates lower units into Types A–D by reverse capability, shift arrangement, and water-pump location, with propeller removal, gearcase disassembly, bearing and seal service, backlash setup, water-pump repair, assembly, and installation.
• Adds hydraulic trim/tilt bleeding and pump service, Commander shift-control repair, eight hand-rewind starter layouts, model-specific wiring diagrams, torque tables, ignition test charts, and service-tool references.

Match the Correct Mercury Configuration

Coverage is indexed by model and beginning serial number, not just by a blanket year range. The timing chapter uses serial 4709592 as the Model 200 change point. Separate groups cover the Model 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 coverage is further divided by manual or electric start, alternator fitment, and operation 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 Mercury engines are outside this book; some 40 HP models therefore require a different manual.

Fuel, Ignition, and Electrical Systems

Fuel-system coverage starts with float-chamber and air-flow operation, then moves into fault isolation for restricted lines, weak pumps, rough idle, and excessive fuel use. Each carburetor family has its own repair section rather than a single generic overhaul procedure. Separate chapters address fuel-pump pressure checks and the optional oil-injection system, including warning-horn diagnosis, storage preparation, and return-to-service checks.

Ignition work is divided into four systems: the Phelon flywheel magneto, Thunderbolt Phase Maker with points, Thunderbolt pointless capacitor discharge, and Thunderbolt capacitor discharge with one coil per cylinder. The manual pairs those sections with model-specific timing and synchronization procedures, stator and coil test charts, polarity checks, spark testing, and flywheel service. Electrical chapters also cover batteries, charging circuits, solenoids, and both large and small cranking motors.

Internal Engine, Gearcase, Trim, and Controls

The powerhead chapters distinguish a split block with an internal reed box, a split block with an external reed block, and a split block 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.

Lower-unit service follows the same approach. Type A has no reverse gear; Type B adds reverse capability; Type C uses a different shift arrangement; and Type D has no reverse capability with the water pump installed on the propeller shaft. Trim/tilt coverage includes hydraulic bleeding, component testing, cylinder and pump work, solenoid diagnosis, and electric-motor service. The Commander chapter covers shift-box removal, disassembly, inspection, reassembly, cable checks, and installation.

Service-tool callouts include Mercury lockring tool 91-5252A1, lower-unit puller 91-27780, and Quicksilver Multimeter/DVA Tester 91-99750. The repair cautions are equally specific: piston-ring locating pins must remain secure because a rotating ring can catch a cylinder port and break, and a used water-pump impeller must not be installed in the opposite direction because premature failure can result.

Charts, Diagrams, and Shop Reference

The appendix supplies engine and tune-up tables, carburetor jet/elevation data, piston and cylinder specifications, reed-stop openings, lower-unit oil capacities and gear data, backlash tables, stator and coil checks, and component-specific torque specifications. Maintenance chapters also cover corrosion control, below-waterline service, propeller care, winter storage, and freshwater-versus-saltwater service intervals.

Notable illustrations include the Phelon magneto schematic, Thunderbolt Phase Maker functional diagram, charging and cranking circuit diagrams, Type A/B/C powerhead exploded drawings, Type A–D lower-unit assemblies, and exploded views of the hydraulic trim pump and Commander control box. Because this work involves gasoline, high-voltage ignition, rotating flywheels, spring-loaded rewind starters, and hydraulic components, the manual’s isolation and handling precautions should be followed before repair work begins.