The instrument panel

Don't take our word for it. Take your numbers.

Every claim on this site can be tested against your own boat — that's the point of these tools. All indicative, all verified by an engineer before anything is supplied.

Measured data behind every default11,353 fitments on tapNo prices, no games — engineering

Live on every tool — your numbers, not ours

Fuel savings calculator

Your engine, your hours, 2026 diesel prices — the annual dollars, litres, CO₂ and range a propeller change is worth.

A$ · L · CO₂editable defaults

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RPM / speed chart

Two curves, one boat. Drag the cruise line and watch the revs fall — the before/after story, interactive.

drag the cruise linemeasured anchors

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Sailing drag comparison

Fixed vs feathered vs folded, on three identical hulls. See what you're towing.

3 hulls, animatedbucket included

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SigmaDrive selector

Shaft, power, gearbox → coupling model, checked against 250+ documented gearbox flanges.

250+ flangesfactory formula

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Symptom checker

Something's wrong? Pick the symptom — vibration, smoke, weak reverse — and get the cause tree and the free checks first.

10 symptomshonest outcomes

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The WOT test

Sixty seconds at full throttle tells you if you're over-propped. Enter rated vs achieved RPM for the verdict.

60-second checkinstant verdict

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Slip & efficiency calculator

Pitch, ratio, RPM and GPS speed → your slip percentage, and what the number means for fuel.

4 inputsinterpretation bands

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Prop stamp decoder

Type what's stamped on your hub — '16 × 10 RH' — and get the plain-English readout.

instant readoutstart here

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Hull speed explorer

Waterline length → hull speed and the power curve — why the last knot costs triple.

1.34 × √LWLsweet-spot marker

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The main event

The Prop Builder

Your boat checked against 11,353+ documented fitments, sized by the real engineering rules, screened for the risk factors — and verified by a human before anything is supplied.

2 minutesrisk screeningengineer-verified

Build my prop spec