1999 Yamaha 50G, 60F, 70B, 75C, 80A, 90A Outboard Motor Service Manual (P/N 6H2-28197-Z9-11)

Yamaha service manual 6H2-28197-Z9-11, first edition February 1999, covers the 50G, 60F, 70B, 75C, 80A, and 90A outboard families. Its identification tables connect worldwide model names with US and Canadian designations and list starting serial numbers by transom height.

• Power unit repair: Powerhead removal, crankcase disassembly, piston and crankshaft inspection, reed-valve checks, and separate assembly procedures for the two engine families.

• Fuel and lubrication: Carburetor overhaul, fuel-pump inspection, electrothermal-valve testing, oil-injection pump output checks, linkage adjustment, and oil-system bleeding.

• Lower unit service: Gear and bearing replacement, shim selection, forward and reverse backlash measurement, water-pump installation, and gearcase leakage testing.

• Bracket and power trim: Steering-handle and bracket service, trim-sensor adjustment, PTT cylinder repair, hydraulic pressure testing, and air bleeding.

• Electrical diagnosis: CDI peak-voltage tests, crank-position-sensor checks, rectifier/regulator testing, starter-motor overhaul, and model-specific wiring diagrams.

• Maintenance and fault tracing: Maintenance schedule charts, full-retard and pick-up timing adjustments, oil-warning-system checks, and symptom-based Trouble Analysis Charts.

Written primarily for Yamaha dealers and trained mechanics, this manual assumes a basic understanding of the mechanical and electrical procedures involved.

Carburetor Variants and Powerhead Repair

Fuel-system differences: C60ER, C60TR, and C75TR carburetors have separate exploded views from the electrothermal-valve versions. Premix and oil-injection configurations are distinguished, and the pump-output test addresses lubrication oil. Fuel-filter drawings and carburetor-linkage illustrations support routine service.

The carburetor cautions explain how steel-wire cleaning can enlarge jets and how overtightening can damage the pilot-screw tip.

Internal engine work: Power-unit exploded views show component placement, including the reed valves. Inspection procedures cover cylinder bores, piston clearances, installed ring end gaps, crankshaft deflection, and thermostat operation. Oversize-piston data and separate crank-cylinder assembly procedures support the overhaul sections.

Reference tables include bore and stroke dimensions, compression ratios, wear limits, and staged tightening specifications.

Lower-Unit Shimming and PTT Service Limits

Lower-case exploded views distinguish the shift mechanisms. Shim-selection procedures separate US/Canadian tooling from other-market methods, with worked calculations and adjustment charts.

The backlash notes explain how incorrect readings in both directions can point to pinion height, helping distinguish a pinion-shim issue from an individual gear adjustment. Tool references include bearing puller 90890-06535 and backlash indicator YB-06265 / 90890-06706. Gear-oil capacities are specified by model.

PTT variants: Separate repair sections cover short-transom 6H308 and long-transom 6H1-15 / 62F-02 assemblies, with exploded views and hydraulic circuit diagrams. The factory-adjusted gear pump is replaced as a complete unit; internal pump disassembly is excluded.

The separate pressurized hydraulic tilt cylinder is covered for inspection and replacement, with overhaul expressly prohibited. Support warnings address the risk of a raised outboard dropping during trim-sensor work.

Ignition Tests and Wiring References

The electrical section pairs ignition spark-gap views and CDI, charge-coil, and pulser-coil test tables with lead-color references. Remote-control-box and digital-meter diagrams complement the engine wiring schematics.

Trouble Analysis Charts connect starting, rough-idle, overheating, charging, shifting, and tilt symptoms with the relevant components and manual chapters.

A Preview of Engine Clearances and Ignition Test Data

These examples show a small selection of the manual's inspection and electrical reference data.

Cylinder-head warpage is limited to 0.1 mm across the covered models. Standard piston-to-cylinder clearance is 0.050–0.055 mm for the 50G/60F/70B group and 0.060–0.065 mm for the 75C/80A/90A group.

For the 50G/60F/70B charge coil, the Brown–Blue resistance specification is 136–204 Ω at 20°C (68°F).

PDF Navigation and Included Pages

Text search and diagram detail: The main text is searchable, and bookmarks open the introduction, index, and all nine chapters. The RETURN bookmark points to a separate index file. Small wiring labels require zooming; labels embedded in the wiring images are not searchable.

The download contains one 204-page printable PDF in English. The total already includes the front and back covers and eight blank separator pages.