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Third-party results

What the magazines measured.

Six independent publications, a bench test, a fuel trial and a season-long ownership test — one consistent direction. Summarised faithfully, including what each result does not prove.

YachtingMonthly

Yachting Monthly (UK)

Comparative test of 12 propellers on the same boat

Reported

“Our tests show the Autoprop achieved 6 knots at 2100 rpm compared to 2500 rpm for our standard prop and most of the others on test.” The same programme documented feathered/folded drag at a fraction of fixed-prop drag.

What it means (and doesn't)

The 300–400 rpm cruise reduction isn't marketing arithmetic — it's the measured gap on a controlled boat. Your boat's exact delta depends on hull, engine and gearbox.

Voile Magazine

Voile Magazine (France)

Feathering propeller trials, Sun Odyssey 34.2 — April 2009, p.83

Reported

Autoprop made 5.10 knots at 1,500 rpm where the three rivals managed 3.75–4.20; at six knots it burned 1.40 L/h against their 2.00–2.20. “It ranked first for consumption at cruising speed.”

What it means (and doesn't)

30–36% less fuel than every competitor in the same water on the same day. One boat, one trial — the direction is consistent with every documented result we hold, and it's why our calculator defaults stay conservative.

VELA e MOTORE

Vela e Motore · De Yacht · Seil

Italian, Dutch and Norwegian comparative surveys

Reported

“It demonstrated good speeds under all conditions” (Vela e Motore). “An excessive amount of engine power is always available” (De Yacht). “At RPMs up to 2000 no other propeller can beat the Autoprop” (Seil).

What it means (and doesn't)

Six publications, five languages, one pattern: the self-pitching action shows up wherever someone measures it. The full quotes live in the press file below.

il Giornale della VELA

Il Giornale della Vela (Italy)

Long-term owner test, published 2022

Reported

After a season of real use: fuel consumption down more than 30% on a 75 hp Yanmar for the owner's usage pattern, feathered drag cut by up to 95%, and an immediate, symmetric response going astern.

What it means (and doesn't)

The rare long-term test — not a bench day but a season. One owner, one usage pattern; the 30% figure tracks the Voiles bench numbers from thirteen years earlier.

Plotted

The same results, as charts

Every chart carries a MEASURED or MODELLED badge, its source, and a data table — that's the standard across this site.

Speed at matched revs — four feathering props, same boat

Measured
Voiles Magazine, April 2009 — Sun Odyssey 34.2, 29 hp Volvo, p.83

Fuel burn at 6 knots — same boat, same day

Measured
Voiles Magazine, April 2009 — Sun Odyssey 34.2, 29 hp Volvo, p.83

75 hp Yanmar, season-long test — speed vs revs on the Autoprop

Measured

Solid dots are the published figures — 6.4 kn at 1,000 rpm to 9.5 kn at 3,000 (hull speed, shaded). Owner-reported fuel saving: more than 30%.

Il Giornale della Vela long-term test, 2022 — 75 hp Yanmar; published end points, intermediate curve indicative

How far 10 litres takes you at 6 knots

Measured
Derived from the Voiles fuel figures at 6 knots (10 L ÷ L/h × 6 kn)

Owner-reported numbers

The real-world corroboration

Numbers owners logged on their own boats, from the programme files. Individual vessels and conditions — corroboration of the pattern, not laboratory data.

Boat & propellerReported numbersNet effect
Bavaria 38 — Autoprop2.5–2.75 L/h at 5.5 kn (2,250–2,500 rpm) → just under 2 L/h at 1,800 rpm~20–25% fuel saving
21 ft motor yacht, Atlantic crossing — Autoprop6 kn at 1,250 rpm where the fixed blade needed 1,500 rpmsame hull speed, 250 fewer revs
Oyster 66 (ex Max-Prop) — Varifold 4-blade“Massive” noise reduction; ~20% better fuel efficiency motoringquieter and cheaper to run
132 ft alloy catamaran — Varifold 4-blade pair10+ kn at 1,800 rpm vs 9; holds 8–8.5 kn punching 20 kn wind and ¾ m seas where the old props fell to 6–7~10–20% performance gain
Scanyacht 399DS — Varifold 3-blade, saildrive~7 kn at 2,000 rpm, smoother; blades stay folded above 4.5 kn under sailquieter motoring, cleaner sailing
UFO 31 — Varifold on Beta BD722, 2.7:15.4 kn at 2,400 rpm; windward sailing went from ~5 kn to 6–7 kn in F3–4“should have changed years back”

The press file

In their words

“Our tests show the Autoprop achieved 6 knots at 2100 rpm compared to 2500 rpm for our standard prop and most of the others on test.”

YachtingMonthlyYachting Monthly · 12-propeller comparative test

“The qualities of the Autoprop make it perfect for long distance cruising. It ranked first for consumption at cruising speed.”

Voile MagazineVoile Magazine · Sun Odyssey 34.2 trials, April 2009

“At RPMs up to 2000 no other propeller can beat the Autoprop, it clearly gave more speed.”

SEILSeil · Norwegian comparative test

“A phenomenon across all speeds is the Autoprop. An excessive amount of engine power is always available, because this propeller comes up with optimum efficiencies at any speed.”

De YachtDe Yacht Magazine

“Certainly one of the most interesting propellers in our survey. It demonstrated good speeds under all conditions.”

VELA e MOTOREVela e Motore

“I can highly recommend Autoprop propellers to all sail boat owners who want the very best performance under power and sail.”

Owner reportSir Chay Blyth — The Challenge Business

“Fuel use down more than 30% on a 75 hp Yanmar for my usage pattern — drag cut by up to 95%, and the response astern is immediate and symmetric.”

il Giornale della VELAIl Giornale della Vela · Long-term owner test, 2022 — findings paraphrased

“Perfect.”

Builder's verdictP.G. Johansson, Baltic Yachts — 4-blade Varifold, Baltic 147

“Cavitation noise is much reduced and we're about half a knot faster at the top end — exactly as Bruntons predicted.”

Owner reportCharlie Wroe, captain of Mariette · Classic schooner, Varifold refit — paraphrased from the press file

Our claims policy

Conservative figure first, source named, assumptions visible

We publish the conservative number, attribute bigger figures to the named test or owner, and keep a substantiation file per claim — Australian Consumer Law hygiene, and simply how engineers should talk.

Test it on your boat instead

The pattern holds across the documented fleet — but your boat's numbers are the ones that matter. Two minutes in the Builder.

Build my prop spec0418 327 403