Propeller Shaft and Cutless Bearing Service in Australia

The propeller shaft runs from the gearbox coupling, through the stern gland, and out through one or more cutless bearings to the propeller. Everything outside the hull is below the waterline, so this is haul-out work.

→ Slipway and haul-out engine work

The cutless bearing

A water-lubricated bearing — traditionally rubber-lined, now often composite — supporting the shaft where it exits the hull. Grooves in the lining let water through to lubricate and cool it.

It wears, and the classic test is simple: with the boat hauled, grip the shaft and try to move it vertically. Perceptible play means the bearing is due.

A worn cutless bearing causes vibration, which is frequently blamed on the propeller. It also accelerates wear on everything else in the drivetrain, and a badly worn one can score the shaft.

Wear accelerates with misalignment, with sand and silt in the water, and with a shaft that is bent or scored. → Engine alignment and coupling

The shaft

Corrosion and pitting, particularly where the shaft sits in the bearing and gland.

Scoring at the gland, from an over-tightened packing gland running dry and hot.

Bending, from a grounding, a rope strike, or sustained misalignment. A bent shaft cannot be trued reliably in place — it needs checking on rollers or in a lathe.

Taper and key wear at the propeller end.

Anodes. Shaft anodes waste and need replacing at each haul-out. → Anode inspection and replacement

The propeller

Inspected at the same time for damage, cavitation erosion and pitch accuracy. A propeller that has been repaired badly, or is out of pitch, overloads the engine and produces exactly the symptoms owners attribute to fuel or turbo faults.

→ Won’t reach wide open throttle RPM

Do it all together

The shaft, cutless bearing, stern gland, anodes, propeller and alignment are one system reached through one haul-out. Doing them piecemeal means paying for the lift repeatedly, and a new cutless bearing behind a misaligned engine wears out early anyway.

→ Shaft seal and stern gland service

What it costs

Dominated by the haul-out and by whether the shaft needs work.

Frequently asked questions

How do I know if the cutless bearing is worn? With the boat hauled, try to move the shaft vertically in the bearing. Perceptible play means it is due.

Is my vibration the propeller or the bearing? Either, plus alignment or a bent shaft. All four are checked at the same haul-out, which is why they are done together.

How long does a cutless bearing last? Highly variable — years in clean water with good alignment, far less with sand, silt or misalignment.

Can the shaft be reused if it is scored? Sometimes, depending on where and how deep. Scoring at the gland from an over-tightened stuffing box is common and may be recoverable.

Should I replace the shaft anode every haul-out? Yes, or whenever it is around half consumed.