1994 Yamaha 40T, 50T, 40V, 50H Outboard Motor Service Manual (P/N 63B-28197-Z4-11)

This Yamaha service manual covers the 1994 40T, 50T, 40V, and 50H outboard motors, including the 6H4 and 6H5 model families. It is the first edition, August 1994, P/N 63B-28197-Z4-11, with LIT-18616-01-19 on the cover.

Search, bookmarks, and wiring detail: PDF text search is not available. Chapter and section bookmarks are included, although “Return to main index” points to a separate file that is not included. Small labels in the denser wiring diagrams require zooming.

• Power unit repair: Engine removal and installation, crankcase separation, piston and crankshaft inspection, reed-valve service, and thermostat testing.

• Fuel and oil injection: Carburetor overhaul and synchronization, Prime Starter inspection, fuel-pump checks, and oil-pump linkage adjustment.

• Lower unit: Gearcase repair, water-pump service, propeller-shaft and dog-clutch inspection, shim selection, backlash measurement, and leakage testing.

• Bracket and tilt systems: Manual tilt, hydro tilt, and power trim and tilt assemblies, with tilt-cylinder overhaul, pump-housing disassembly, and PTT motor inspection.

• Electrical diagnosis: CDI, charge-coil, and pulser-coil testing; ignition timing adjustment; starting, charging, warning-circuit, and PTT control checks with wiring diagrams.

• Service data: Maintenance interval charts, tightening torque tables, fluid capacities, wear limits, electrical test specifications, and dimension drawings.

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

Fuel System and Power Unit Repair

The fuel sections distinguish choke-equipped manual-start models from Prime Start configurations. Carburetor identification tables separate the 40 HP and 50 HP M, E, and EM versions, while Fuel Line Layout and Oil Line Layout illustrations show the corresponding hose routing.

Carburetor service includes float and needle-valve inspection, pilot-screw adjustment, and throttle synchronization. The repair notes explain how cleaning jets with steel wire can enlarge their openings and affect engine performance.

The Power Unit chapter covers the loop-charged, 3-cylinder 2-stroke engine through cylinder-body, piston-pin, small-end bearing, and crankshaft inspection. Factory specifications include cylinder bore sizes, piston clearances, ring wear limits, and cylinder-head warpage.

Recoil starter and flywheel magneto work have dedicated removal and service instructions. Electrical Unit removal and disassembly are also covered, alongside reed-valve, check-valve, and thermostat inspection.

Lower Unit Repair and Shimming

Separate procedures address pinion, forward-gear, and reverse-gear shim selection, with different measuring tools for U.S./Canada and other markets. The selection guide distinguishes reusing the original components, replacing the gearcase, and replacing internal parts. This helps identify which measurements are required for the particular rebuild.

The tool references include backlash indicator YB-06265 / 90890-06706 and dial indicator YU-03097 / 90890-01252. Exploded diagrams and removal/installation charts identify the bearing, seal, and shift components, including the extension used on UL models.

Bracket Unit and Power Trim and Tilt

Bracket procedures distinguish manual tilt, hydro tilt, and PTT hardware. Hydraulic repair coverage extends to the inner cylinder, tilt piston, gear pump, manual valve, and shuttle piston. PTT motor checks cover the brushes, commutator, armature, and circuit breaker.

The inner-cylinder procedure warns that incorrect clamping can deform the cylinder. PTT fluid servicing and disassembly also address trapped hydraulic pressure and the risk of fluid ejection.

Electrical Testing and Troubleshooting

Named circuit diagrams include Ignition System, Ignition Control System, Starting System, and Power Trim and Tilt Control System. They distinguish manual and electric starting and the different oil-warning arrangements, with wire-color codes and coupler layouts.

CDI testing separates control-unit output from charge-coil and pulser-coil output, helping narrow an ignition fault before a component is replaced. Other checks cover the rectifier regulator, electrothermal valve, oil-level sensor, starter relay, and trim sensor.

The Trouble Analysis Chart connects symptoms such as failure to start, rough idling, overheating, hard shifting, and an inoperative tilt motor to the relevant components and service chapters.

English PDF and Included Pages

Supplied as one printable English PDF. The 213-page total includes one cover, six introductory, symbol, and index pages, and 206 pages covering the nine service chapters and their contents pages.