Manufacturer
Yamaha 4hp
Japanese manufacturer of marine propulsion and boat-control systems, including electric propulsion products.
Official manufacturer website ↗
4hp
The 4hp might look compact, but it's got the heart of a heavyweight. Smooth, steady and ready for anything, it's proof that size isn't everything… but balance just might be.
Key facts
- Family: Portable
- Engine type: OHV, 1-cylinder
- Displacement: 139 cm³
- Rated output: 2.9 kW
- Weight: S: 27 kg, L: 28 kg
- Operating range: 4000 – 5000 r/min
- Fuel system: 1 carburetor
Position in Yamaha range
The Portable family is focused on lower-output engines where mass, handling, storage and simple installation are key considerations.
This is model 4 of 5 in the Portable family when the range is ordered from higher to lower rated output.
Neighbouring models
Before choosing
Verify the boat manufacturer’s permitted power range, transom height and shaft length, engine and rigging weight, steering and control compatibility, electrical load, propeller selection and the exact variant code before ordering. For twin or multiple-engine installations, confirm steering and control-system requirements as a complete package.
FAQ
- Is this the same as another Yamaha model with similar horsepower?
- Not necessarily. Yamaha can offer different families, control systems, shaft lengths, rotations or duty-oriented variants at a similar output. Compare the full specification rather than horsepower alone.
- What should be verified before installation?
- Confirm shaft or mounting configuration, steering and controls, electrical requirements, propeller selection, weight and the exact model or variant code.
Sources & verification
Technical data: Yamaha Motor Europe official product page. Official factsheet. Verified: 2026-09-06.
Engine
| Engine type | OHV, 1-cylinder |
|---|---|
| Displacement | 139 cm³ |
| Bore x stroke | 62.0 × 46.0 mm |
| Compression ratio | 8.9 : 1 |
| Fuel induction system | 1 carburetor |
| Lubrication system | Wet sump |
| Engine oil capacity | 0.6 L |
| Ignition / advance system | CDI |
| Alternator | 6 A with optional regulator |
Dimensions
| Overall length | 750 mm |
|---|---|
| Overall width | 403 mm |
| Overall height | S: 1039 mm, L: 1166 mm |
| Engine transom height | S: 435 mm, L: 562 mm |
| Steering angle | 90 degrees each direction |
| Dry weight | S: 27 kg, L: 28 kg |
Performance
| Maximum propeller shaft output | 2.9 kW |
|---|---|
| Full throttle operating range | 4000 – 5000 r/min |
| Idling speed | 1450 – 1550 r/min |
Bracket/Drive
| Shallow water drive | 3 positions |
|---|---|
| Gear shift | F-N-R |
| Gear ratio | 2.08 (27/13) |
| Gear oil capacity | 0.100 L |