Monohull · 28 documented fitments
Propeller upgrade for the Sigma 33 — what fits, what changes.
Drawn from 28 documented Sigma 33 fitments: the common setup is a Varifold 2-blade behind the Beta Marine 25. Typical result: 300–400 fewer RPM at cruise and up to 20% fuel saved over fixed pitch.
The fitment card
Documented engine variants & what they wear
Aggregated from 28 real installations — not a size chart, a service record.
| Engine | Power / max RPM | Drive | Typical ratio | Documented propeller | Rotation | Records |
|---|---|---|---|---|---|---|
| Beta Marine 25 | 25 hp / 3600 | Shaft | 2:1 | Varifold 2-blade | Right-hand | 13 |
| Beta Marine | 20 hp / 3600 | Shaft | 2:1 | Varifold 2-blade | Right-hand | 5 |
| Beta Marine 20 | 20 hp / 3600 | Shaft | 2:1 | Varifold 2-blade | Right-hand | 2 |
| Volvo Penta 2002 | 18 hp / 3200 | Shaft | 2.4:1 | Varifold 2-blade | Left-hand | 2 |
| Vetus 206 | 158 hp / 3600 | Shaft | 2.6:1 | Varifold 2-blade | Right-hand | 1 |
| Beta Marine BD722 | 20 hp / 3600 | Shaft | 2.33:1 | Varifold 2-blade | Right-hand | 1 |
| Volvo Penta PENTA 2002 | 18 hp / 3200 | Shaft | 2.37:1 | Varifold 2-blade | Left-hand | 1 |
| Yanmar 3YM20 | 21 hp / 3600 | Shaft | 2.21:1 | Autoprop H5 | Right-hand | 1 |
Plus 1 less common variants in the database. Indicative only — gearboxes and apertures vary between years and repowers, which is why every supplied propeller is verified against your boat first. Data current as of 2026.
Your numbers
What the change feels like on a Sigma 33
Indicative curves for this size of boat — drag the cruise line. The independent-test pattern: the same six knots on several hundred fewer RPM, with the fuel flow following.
Worth knowing
Considerations for the Sigma 33
- 9 engine variants are documented for this model — repowers included. Sizing follows your engine and ratio, not the year in the brochure.
- Tip clearance rules the maximum diameter — roughly 10–15% of prop diameter to the hull. The Builder asks; we verify before supply.
Sigma 33 propeller questions
What size propeller does a Sigma 33 take?
Documented Sigma 33 installations most commonly run a Varifold 2-blade, matched to the Beta Marine 25 on a shaft drive. Exact size depends on your engine, gearbox ratio and aperture — every recommendation is verified by an engineer before supply.
How much fuel would a Sigma 33 save with an Autoprop?
Typical savings over a fixed-pitch propeller are up to 20% at cruise (documented band 15–30%, honestly less if you already run a folding or feathering prop). Put your engine hours and diesel price into the fuel calculator for your own numbers — then the Builder for a verified recommendation.
My Sigma 33 has a different engine than shown — does the data still help?
Yes. Repowers are common and the database usually holds several engine variants per model. The Builder starts from your actual engine and gearbox; the model records confirm diameters and clearances that are known to work on this hull.
Get the verified recommendation for your Sigma 33
The Builder pre-fills from these 28 documented fitments — confirm your engine and gearbox, and an engineer replies within one business day.