Yamaha 1989-94 40 HP Outboard Specs & Maintenance
The 1989–1994 40 HP 3-cylinder 2-stroke outboard is a workhorse revered by vintage boating enthusiasts. Packing a punch with its 43 cu. in. (698 cc) inline displacement, this engine balances smooth three-cylinder power with legendary two-stroke reliability. Whether you’re restoring a classic skiff or maintaining your daily angler, our comprehensive technical database provides the factory specs, tuning guidance, and maintenance data needed to keep your trusted 40-horse running strong on the water.
Complete Technical Specifications
| Specification | Details |
|---|---|
| Model / Horsepower | 40 |
| Year Range | 1989-94 |
| Engine Type | IL 2-stroke |
| Cylinders | 3 |
| Displacement | 43 cu-in (698 cc) |
| Bore x Stroke | 2.64 x 2.60 in (67 x 66 mm) |
| Compression Ratio | 6.0:1 |
| Full Throttle RPM | 4500-5500 |
| Idle Speed (Neutral) RPM | 750-850 |
| Idle Speed (Trolling) RPM | 550-650 |
| Spark Plug (NGK) | B7HS-10 |
| Spark Plug (Champion) | L82C |
| Spark Plug Gap | 0.035-0.039 in (0.9-1.0 mm) |
| Ignition System | CDI |
| Ignition Timing (Idle) | 4-6 ATDC |
| Ignition Timing (Carb Pickup) | 4-6 ATDC |
| Ignition Timing (Full Advance) | 24-26 |
| Fuel System | Carb |
| Starting System | Manual and/or Elec |
| Oil Injection System | PB or 50:1 PM |
| Injection Oil Ratio | PB or 50:1 PM |
| Gear Oil Capacity (mL/cc) | 430 |
| Gear Oil Capacity (Oz) | 14.5 |
| Approximate Weight | 149-198 lbs (68-90 kg) |
| Battery CCA / Reserve | 380 (70) |
| Battery Reserve | 124 minutes |
| Tach Pole Setting | 6 |
| Test Propeller Part Number | YB-1611 |
| Test Propeller New Engine RPM | 4900-5100 |
Maintenance Summary
Keep this 698cc inline-three firing smoothly with simple DIY maintenance. Always run fresh fuel-oil mix and inspect the water pump impeller annually. For optimal performance and crisp ignition, set three fresh NGK B7HS-10 spark plugs to a 0.035–0.039 in (0.9–1.0 mm) gap.
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Notice: Specifications, fuel ratios, and maintenance guidelines listed on VintageMotorSpecs.com are compiled for historical reference and educational purposes only.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.
Spot an error or discrepancy in these specs? Please contact us with your engine details so we can update our database.
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