What a spun hub is

Most props isolate the blades from the prop shaft with a rubber or composite hub designed to slip on impact instead of breaking the gearcase. After a strike (or just age), the hub can slip permanently: the engine revs, the boat barely moves — like a slipping clutch.

Confirming it in the field

1. Symptoms: rpm climbs but speed doesn't, especially under hard acceleration; often fine at low throttle.
2. Paint or marker a straight line across the hub face and blade barrel. Run the boat under load. If the line breaks alignment, the hub slipped — diagnosis done.
3. Rule out the impostors: ventilation from a damaged or too-high-mounted prop, a badly fouled bottom, or an actual gearcase clutch problem (listen for grinding/ratcheting — that's a different article and a bigger bill).

Replacement options

• Pressed rubber hubs: need a hydraulic press with the right adapters — usually a prop-shop job, not a dockside one. Many mobile techs carry a loaner prop instead.
• Cartridge/insert systems (common on modern props): the hub kit slides out and a new one installs with hand tools — very field-friendly. Match the kit to the prop and spline count.
• Genuinely damaged blades go to a prop shop for reconditioning; bent blades cause vibration that eats gearcase seals.

Removal and installation

1. Kill switch off, key out, battery disconnected — you are putting hands on the prop.
2. Block the blades with a wood block (never your hand) to break the prop nut loose. Note the stack order: thrust washer, prop, spacer, washer, nut — photograph it.
3. Clean the shaft splines and inspect for fishing line at the seal — every single time.
4. Grease the splines with marine grease to prevent the prop seizing on the shaft.
5. Reassemble the stack in order, torque the prop nut per the service manual, and install a new cotter pin or bend the tab washer — never reuse a tired cotter pin.

Common mistakes

• Missing thrust washers (prop walks back and eats the gearcase or the shaft threads)
• Un-greased splines — next season's seized-prop call is you
• Torquing the nut by feel and skipping the cotter pin
• Blaming the hub when the real issue is ventilation from a mangled leading edge

When to walk away

Ratcheting or grinding on acceleration with a proven-good prop means clutch dog wear inside the gearcase — quote a teardown, don't sell a hub kit that won't fix it.