Monohull · 22 documented fitments
Propeller upgrade for the Sigma 38 — what fits, what changes.
Drawn from 22 documented Sigma 38 fitments: the common setup is a Varifold 2-blade behind the Yanmar 3YM30. 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 22 real installations — not a size chart, a service record.
| Engine | Power / max RPM | Drive | Typical ratio | Documented propeller | Rotation | Records |
|---|---|---|---|---|---|---|
| Yanmar 3YM30 | 29 hp / 3600 | Shaft | 2.62:1 | Varifold 2-blade | Right-hand | 7 |
| Volvo Penta 2003 | 28 hp / 3200 | Shaft | 2.37:1 | Varifold 2-blade · 406 mm | Left-hand | 5 |
| Volvo Penta D1-30 | 29 hp / 3200 | Shaft | 2.35:1 | Varifold 2-blade | Right-hand | 3 |
| Volvo Penta MD2030 | 29 hp / 3600 | Shaft | 2.4:1 | Varifold 2-blade | Left-hand | 2 |
| — 2003 | 28 hp / 3200 | Shaft | 2.37:1 | Varifold 2-blade | Left-hand | 1 |
| Beta Marine BV1305 | 35 hp / 3600 | Shaft | 2:1 | Varifold 2-blade | Right-hand | 1 |
| Beta 28 28 | 28 hp / 3600 | Shaft | 2.6:1 | Varifold 2-blade | Right-hand | 1 |
| Beta Marine 28 | 28 hp / 3600 | Shaft | 2.33:1 | 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 38
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 38
- 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 38 propeller questions
What size propeller does a Sigma 38 take?
Documented Sigma 38 installations most commonly run a Varifold 2-blade, matched to the Yanmar 3YM30 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 38 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 38 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 38
The Builder pre-fills from these 22 documented fitments — confirm your engine and gearbox, and an engineer replies within one business day.