Yamaha 1989-95 40 HP Outboard Specs & Maintenance
Built between 1989 and 1995, this classic 40 HP 2-cylinder, 2-stroke outboard motor remains a beloved workhorse for lightweight skiffs and utility boats. Pushing out reliable power from its 36 cubic inch (592 cc) inline displacement, it offers an incredible power-to-weight ratio. Whether you are troubleshooting ignition issues or conducting seasonal tune-ups, our comprehensive technical database provides the exact specs, service manual procedures, and maintenance guidance DIY mechanics need to keep this twin-cylinder running strong.
Complete Technical Specifications
| Specification | Details |
|---|---|
| Model / Horsepower | 40 |
| Year Range | 1989-95 |
| Engine Type | IL 2-stroke |
| Cylinders | 2 |
| Displacement | 36 cu-in (592 cc) |
| Bore x Stroke | 2.95 x 2.64 in (75 x 67 mm) |
| Compression Ratio | 6.5:1 |
| Full Throttle RPM | 4500-5500 |
| Idle Speed (Neutral) RPM | 1100-1200 |
| Idle Speed (Trolling) RPM | 950-1050 |
| Spark Plug (NGK) | B8HS |
| Spark Plug (Champion) | L78C |
| Spark Plug Gap | 0.020-0.24 in (0.5-0.6 mm) |
| Ignition System | CDI |
| Ignition Timing (Idle) | 1-3 |
| Ignition Timing (Carb Pickup) | 5 |
| Ignition Timing (Full Advance) | 21-23 |
| Fuel System | Carb |
| Starting System | Man or Man & Elec |
| Oil Injection System | Pre-Mix 100:1 |
| Injection Oil Ratio | Pre-Mix 100:1 |
| Gear Oil Capacity (mL/cc) | 315 |
| Gear Oil Capacity (Oz) | 10.7 |
| Approximate Weight | 133-165 lbs (61-75 kg) |
| Battery CCA / Reserve | 385 (70) |
| Battery Reserve | 124 minutes |
| Tach Pole Setting | 4 |
| Test Propeller Part Number | YB-1611 |
| Test Propeller New Engine RPM | 4600-4800 |
Maintenance Summary
Keeping this 40 HP 2-stroke healthy requires basic routine care. Ensure optimal ignition performance by running fresh NGK B8HS spark plugs gapped precisely to 0.020-0.024 inches (0.5-0.6 mm). Regularly inspect the water pump impeller, maintain a fresh 50:1 fuel mixture, and change the lower unit lube seasonally.
Disclaimer & Information Notice: Specifications, fuel ratios, and maintenance guidelines listed on VintageMotorSpecs.com are compiled for historical reference and educational purposes only. Always verify data against an official OEM service manual prior to ordering parts or executing repairs. VintageMotorSpecs.com assumes no liability for repair errors, equipment damage, or personal injury resulting from the use of this data.
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