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BRUNTONSAustralia

Symptom diagnosis

Propeller keeps spinning under sail — stop a freewheeling shaft

That whirr under the aft bunk on passage is the shaft turning with nobody driving. It wears the gearbox (which may not be lubricated at rest), and it stops low-drag propellers folding or feathering.

  1. 1. Hydraulic gearbox that can't self-lock

    most likely

    Hydraulic boxes need oil pressure to hold gear — engine off means no pressure, so the shaft spins free. Locking it in gear does nothing.

    Do thisAutolock applies a spring brake automatically at engine-off and releases at start — nothing to remember.

    How Autolock works →

  2. 2. Mechanical box owners: just engage reverse

    common

    Most mechanical gearboxes can be locked in reverse under sail (check your manual). If yours can, the fix is free.

    Do thisCheck the gearbox manual first — this page may cost you nothing.

  3. 3. The propeller needs the shaft stopped

    worth checking

    Feathering and folding props only deploy on a stationary shaft — a spinning Varifold can't fold, a spinning Autoprop can't feather. The brake unlocks the drag saving you already paid for.

    Do thisPair the brake with the low-drag prop; that's the whole system.

    What the drag is costing →

Before you spend money

If you have a mechanical gearbox, read the manual before buying anything — many lock in reverse for free. The brake is for hydraulic boxes, where there is genuinely no other way.

Other symptoms

Engine won't reach max RPMBlack smoke under loadVibration at cruising revs

Want the numbers checked properly?

Tell the Builder about this symptom — it screens for it, and an engineer reviews every recommendation before anything is supplied.

Build my prop spec0418 327 403