Which outboard for a RIB? Power, shaft length and propeller
The outboard decides how the RIB handles, how much fuel it uses and whether you need a licence. You choose it by three things: power, shaft length and steering.
How much power?
Every boat has a stated maximum outboard power (on the CE plate and in the specifications). That does not mean you have to fit the most powerful outboard. There are three typical choices:
| Choice | Power as % of maximum | Speed | Fuel consumption |
|---|---|---|---|
| Economical | 40–60% | up to about 60% of maximum | low |
| Optimal | 60–80% | up to about 90% of maximum | reasonable |
| Maximum | 80–100% | 100% | highest |
We most often recommend the optimal choice — about 80% of maximum power: the boat is nearly as fast as it can be, safe and not too thirsty. Never exceed the maximum power — it is dangerous, illegal and voids the warranty.
Power and the licence
In Poland you can drive a boat with an outboard up to 10 kW (about 13.6 HP) — in practice 9.9 HP — without a licence. A more powerful outboard requires a motorboat licence (patent motorowodny). More in the guide Motorboat licence.
Typical power for GRAND RIBs
- 2.75–3 m (S275, S300): 2.5–15 HP
- 3.3 m (S330, G340): 5–30 HP
- 3.7 m (S370, G380): 10–40 HP
- 4.2 m (S420, G420): 20–60 HP
- 4.7 m (S470): 25–70 HP
The exact range for each model is on its page, and ready packages with prices are on the Inflatable boat with engine page.
Shaft length
The shaft length is matched to the boat’s transom height:
| Shaft | Transom height |
|---|---|
| S — short | 381 mm / 15″ |
| L — long | 508 mm / 20″ |
| X — extra long | 635 mm / 25″ |
Once fitted, the outboard’s anti-cavitation plate should sit 25–50 mm below the lowest point of the transom. You will find each model’s transom height in its specifications.
Tiller or console steering?
- Tiller — simpler, lighter and cheaper; good for tenders and Open-version RIBs. With us, fitting a tiller outboard is included in the outboard’s price.
- Console (remote-controlled outboard) — more comfortable and safer at higher power, and it spreads the weight better in the boat. It needs a rigging kit (control box, cables, gauge), whose price includes fitting.
How to choose the propeller?
The outboard comes with a standard propeller, but the best performance comes from a propeller matched to the boat and the load. Check the rpm at full throttle with a typical load: if it is below the outboard’s recommended range, choose a propeller with a lower pitch; if the outboard reaches it too easily, choose a higher pitch. It is worth having two propellers: one for heavy loads and one for a light boat. We will choose the propeller when fitting the outboard in our service centre.
Example Yamaha outboard prices
- 2.5 HP — 4 100 zł
- 9.9 HP — 12 500 zł
- 25 HP — 22 500 zł
- 40 HP — 26 200 zł
- 70 HP — 40 500 zł
All outboards are in the Yamaha outboards section. They carry a Yamaha 3 + 2-year warranty.
Frequently asked questions
Which outboard for a RIB without a licence?
Up to 10 kW, which usually means 9.9 HP.
Can I fit an outboard more powerful than the maximum?
No — it is dangerous, against the regulations and voids the warranty.
2-stroke or 4-stroke?
The Yamaha outboards we offer are modern 4-strokes: quieter, more economical and cleaner.
