1994–2001 Yamaha 4M, 4AC/4MH, 4AS, 5C & 5CS Outboard Service Manual (P/N 6E0-28197-23-F1)

This Yamaha service manual covers the 4AC (4MH), 4AS, 5C, and 5CS two-stroke outboards, with the 1994–2001 4M model codes listed on the cover. Publication P/N 6E0-28197-23-F1, first edition August 1993, documents manual-start, tiller-controlled configurations.

Text search, bookmarks, and diagram detail: OCR text search is available, with bookmarks for the English chapters and individual procedures. Recognition errors can affect exact search matches. Small wiring labels and CDI resistance tables are best read enlarged.

• Power unit repair: Engine removal and installation, cylinder and piston inspection, crankshaft bearing replacement, reed-valve checks, and crankcase reassembly.

• Fuel system: Built-in and separate fuel-tank service, carburetor overhaul, diaphragm fuel-pump repair, float-height adjustment, and throttle-wire adjustment.

• Lower unit and cooling: Water-pump impeller replacement, gearcase and shaft repair, clutch-dog inspection, lower-unit leakage testing, and thermostat testing.

• Starter and brackets: Recoil-starter rebuilding, bracket-unit overhaul, steering-handle repair, and start-in-gear protection adjustment for applicable non-European versions.

• CDI diagnostics: Charge-coil and low- and high-speed pulser-coil tests, ignition-coil checks, stop-switch continuity tests, wiring diagrams, and CDI test charts.

• Maintenance and fault finding: Service schedules, compression testing, ignition-timing checks, and troubleshooting charts for starting problems, rough running, power loss, misfiring, and shifting faults.

Yamaha wrote this manual primarily for its dealers and their trained mechanics, assuming an understanding of the mechanical and electrical work involved.

Fuel-Tank Layouts and Carburetor Repair

The fuel chapter separates the built-in-tank 4AC/4MH and 5C models from the separate-tank 4AS and 5CS versions. Separate-tank coverage includes the priming pump, fuel-hose joints, filter, and joint pressure testing, with different illustrations for European and Oceania equipment.

Carburetor exploded views and job instruction charts cover the fuel-pump diaphragms, needle valve, pilot screw, float, and jets. The cleaning notes warn that steel wire can enlarge jet openings and affect engine performance.

Power Unit, Recoil Starter, and Service Data

Power-unit inspection covers cylinder wear, piston-to-cylinder clearance, piston rings, and crankshaft runout. The repair sections also address the drainless mechanism and its check valves, oil-seal housings, and crankshaft main bearings.

Flywheel removal specifies puller YB-6117 / 90890-06521 and explains how uneven puller loading can damage the crankshaft or tools. Recoil-starter coverage extends to the drive pawl, sheave drum, starter rope, and return spring.

Reference tables provide lubricant capacities, gear backlash, spark-plug specifications, and tightening torques for the crankcase, cylinder-head cover, and gearcase. Thermostat inspection includes opening-temperature and valve-lift checks.

Lower Unit, Water Pump, and Bracket Unit

Lower-unit section diagrams identify the additional casing and bearing components used on long-shaft models. Gearcase procedures cover forward and reverse gears, the shift plunger, bearings, bushings, and shaft seals, followed by gear-shift checks and an air-leakage test.

Bracket-unit procedures cover the upper casing, bottom cowling, and water tube. Clamp and swivel brackets, steering-friction parts, the tilt-lock mechanism, and the steering handle have their own disassembly and inspection coverage.

CDI Testing and Troubleshooting

The ignition system uses separate low- and high-speed pulser coils with electronic spark advance. Wiring and lead-routing diagrams, an ignition-advance graph, and the CDI resistance matrix support the electrical checks.

Test equipment matters: CDI-unit resistance testing specifies an analog meter. The separate USA/Canada procedures use the Y-1 ignition tester, YU-91022-B, for CDI, charge-coil, and pulser-coil output tests. These component-specific tests help isolate the source of a weak spark before parts are replaced.

Troubleshooting flowcharts connect fuel delivery, spark, and compression checks to starting and running symptoms. A separate chart addresses shift-linkage faults and internal gearcase problems.

Work in a well-ventilated area and follow the manual's precautions for gasoline, rotating parts, and high-voltage ignition components.

Multilingual PDF and Included Pages

This printable 449-page PDF contains English, German, French, and Italian text. The total comprises 447 manual pages, including introductory material and publication details, plus the one-page model-list cover and one-page Yamaha Motor Canada contact sheet.