A one-page checklist of what to inspect on every slipping — plus the five things that are cheap now and ruinous later.

Why a checklist helps

Stern gear problems rarely announce themselves. A cutless bearing wears gradually; an anode disappears quietly; a shaft seal drips a little more each month. The engines-on-top-of-engines mentality that keeps outboards running doesn’t quite fit inboard shafts, so this is a short checklist for your next slipping or your workshop day.

Propeller — inspection points

• Blade edges — look for nicks, erosion, bent tips.
• Blade root — hairline cracks appear here first.
• Hub — fit on taper, keyway wear.
• Nut and split pin — torque to spec, new split pin.
• Zinc anode on hub — replace at <50% remaining.

Measure diameter and pitch of each blade. Variations of more than 1° blade-to-blade mean a trip to the propeller shop.

Cutless bearing — the wear test

With the propeller off, grab the shaft at the stern tube and try to lift it. A good cutless bearing lets the shaft lift roughly 0.5–1 mm. More than 1.5 mm, and the bearing is worn. Replace before the next trip — a worn bearing lets the shaft whip and will chew the shaft and the next bearing in minutes.

Shaft seal

• Face-type seal: Carbon face thickness > 3 mm. No weeping with the shaft turning.
• Stuffing box: Re-pack annually. The shaft under the packing should be smooth.

Shaft itself

Run a dial gauge against the shaft near the coupling. More than 0.1 mm total indicated run-out and the shaft is bent. On the taper, check for fretting — a sign the propeller nut has been loose.

Coupling and alignment

Check the engine-shaft coupling for a 0.05 mm feeler gap all round. More than that and the alignment is out — re-shim before leaving the slip.

Anodes

Shaft anode, rudder anode, hull anode. All three should show less than 50% consumption at every slipping. If one is going fast and another barely at all, there may be a bonding problem — investigate before the next haul.

The five cheap jobs

1. New propeller nut split pin — $0.50.
2. New shaft anode — $35.
3. Fresh grease in grease-type seal cup — $10.
4. New propeller key if any sign of wear — $25.
5. Fresh paint on bonding wires — $5.

Together: under $100. Skipping any of them has sunk boats.

Need advice on your boat’s stern gear or propeller? Call Brian directly on 0413 771 090 or use the contact form — we respond the same day.