Yamaha 1990-96 25 HP Outboard Specs & Maintenance
Built between 1990 and 1996, this 25 HP 2-stroke inline twin-cylinder outboard motor remains a favorite among DIY marine mechanics and boaters alike. Packing a punch with its compact 26 cu. in. (430 cc) displacement, this lightweight workhorse delivers exceptional power-to-weight performance for small skiffs and utility boats. Whether you are performing routine tune-ups or a complete overhaul, our comprehensive specs will help keep your classic twin running smoothly on the water.
Complete Technical Specifications
| Specification | Details |
|---|---|
| Model / Horsepower | 25 |
| Year Range | 1990-96 |
| Engine Type | IL 2-stroke |
| Cylinders | 2 |
| Displacement | 26 (430) |
| Bore x Stroke | 2.64 x 2.40 cu-in (67 x 61 cc) |
| Compression Ratio | 7.0:1 |
| Full Throttle RPM | 4500-5500 |
| Idle Speed (Neutral) RPM | 1150-1250 |
| Idle Speed (Trolling) RPM | 800-900 |
| Spark Plug (NGK) | B7HS-10 |
| Spark Plug (Champion) | L82C |
| Spark Plug Gap | 0.024-0.028 in (0.6-0.7 mm) |
| Ignition System | CDI |
| Ignition Timing (Idle) | 1-3 ATDC |
| Ignition Timing (Carb Pickup) | — |
| Ignition Timing (Full Advance) | 23-25 |
| 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) | 180 |
| Gear Oil Capacity (Oz) | 6.1 |
| Approximate Weight | 106-115 lbs (48-52 kg) |
| Battery CCA / Reserve | 245 (40) |
| Battery Reserve | 59 minutes |
| Tach Pole Setting | 4 |
| Test Propeller Part Number | YB-1621 |
| Test Propeller New Engine RPM | 4200-4400 |
Maintenance Summary
Keeping your 1990–1996 25 HP engine in peak condition requires simple, consistent maintenance. Ensure reliable ignition by running properly torqued NGK B7HS-10 spark plugs, gapped precisely to 0.024–0.028 inches (0.6–0.7 mm). Regularly inspect the water pump impeller and change the lower unit lube seasonally to ensure long-term reliability.
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Notice: Specifications, fuel ratios, and maintenance guidelines listed on VintageMotorSpecs.com are compiled for historical reference and educational purposes only.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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