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FINDINGS LIBRARY · UNDERWATER GEAR

Worn cutless bearing: how to check shaft play and how surveyors write it up

UPDATED 6 NOVEMBER 2026 · 3 EXAMPLE FINDINGS · 2 SOURCES

How a surveyor checks a cutless bearing for play, what 1/16 inch of movement means, what uneven wear says about alignment, what replacement involves and three example findings graded A, B and C.

AT A GLANCE
Worn cutless bearing
USUAL GRADE
A for a shaft that knocks in the bearing or a bearing loose in its strut. B for visible wiggle or an audible thunk when the shaft is shaken. C for slight play of about 1/16 inch, which Practical Sailor calls borderline
FOUND WITH
Grabbing the propeller or shaft with the boat hauled and shaking it firmly up and down and side to side, looking at the bearing ends and the strut, and feeling for vibration in gear on the sea trial
JUDGED AGAINST
Play and wear pattern. Good Old Boat names vibration in gear and 1/16 inch or more of shaft play as the signs of a worn bearing
REPAIR COST
The bearing itself is cheap. The cost is the labour, and it rises sharply if the shaft has to come out or the rudder has to drop to clear it. Priced per boat

The cutless bearing holds the propeller shaft where it leaves the hull, in the stern tube or the P-bracket. It's a brass or composite tube with a grooved rubber lining, lubricated by the water flowing through it. As the lining wears, the shaft gets room to move, the propeller hammers the bearing, and the vibration travels up the shaft to the coupling and the gearbox.

How a surveyor checks it

With the boat out of the water, Practical Sailor's test is simple: grab the propeller or shaft and give it a couple of good, firm shakes. Slight movement, about 1/16 inch, is borderline. A visible wiggle, or a thunk you can hear, means it's due.

Look at the ends of the bearing where you can see the lining. Practical Sailor points to uneven wear, on top at one end and on the bottom at the other, as a sign of significant shaft misalignment. Check the bearing shell is tight in its bracket and the bracket is tight on the hull.

On the sea trial, Good Old Boat's other sign: vibration when in gear.

What decides the grade

How loose it is, and what's loose. A shaft that knocks, or a bearing moving in the bracket, is an A. A visible wiggle or a thunk is a B, to change at the next haul-out. Slight play with even wear is a C to watch.

Worn cutless bearing: example findings

The same defect written up at each grade, the way Axsail writes it from what the surveyor says on board. The grade follows what was found, so use these as wording, then grade what you see.

PROPULSIONA
Propeller shaft, P-bracket bearing

Shaft knocks audibly in the cutless bearing when shaken by hand at the propeller. Rubber lining worn through at the aft end; bearing shell moves in the bracket.

Recommendation: Replace the cutless bearing, check the bracket and its fastenings, and check engine to shaft alignment before the vessel is next underway under power.

PROPULSIONB
Propeller shaft, stern tube bearing

Visible wiggle when the shaft is shaken firmly at the propeller. Lining worn on top at the forward end and on the bottom at the aft end. Vibration felt in gear on the sea trial.

Recommendation: Replace the cutless bearing and check engine to shaft alignment within 12 months, at the next haul-out.

PROPULSIONC
Propeller shaft, P-bracket bearing

Slight movement of about 1/16 inch when the shaft is shaken firmly. Lining even, no vibration on the sea trial.

Recommendation: Monitor the bearing and check the play at the next haul-out.

ASafety. Safety or compliance deficiency. Fix before the vessel is next underway.
B12 months. Deficiency that needs timely attention. Fix within about 12 months.
CRoutine. Note or observation, cosmetic or maintenance. Routine maintenance at the owner's convenience.

What replacement involves

Job Reported cost
Cutless bearing Relatively inexpensive, Good Old Boat
Replacing the bearing with the shaft in place Yard labour, on the hard
Pulling the shaft to replace it More labour; on some boats the rudder must drop to clear the shaft
Alignment check after Mechanic's time

Fix the cause. If the wear pattern points to misalignment, check the engine mounts and align the engine to the shaft before the new bearing goes in; see failed engine mounts.

Photos to take

The bearing ends showing the lining, the bracket and its fastenings, and a short video of the shaft moving if it does. With Axsail, say how far the shaft moved as you take the photo and it goes on the propulsion finding.

Writing it up

Name the bearing by position, how much the shaft moved when shaken and whether it knocked, the wear pattern on the lining, the state of the bracket and any vibration on the sea trial. If the wear points to misalignment, say so and recommend the alignment check.

Frequently asked

How do I check a cutless bearing for wear?

With the boat hauled, grab the propeller or the shaft and give it a couple of firm shakes, Practical Sailor advises. Slight movement of about 1/16 inch is borderline. A visible wiggle or an audible thunk means the bearing is due for replacement.

How much play is too much in a cutless bearing?

Good Old Boat names 1/16 inch or more of shaft play, with vibration in gear, as the signs of a worn bearing. Practical Sailor calls about 1/16 inch borderline and replaces on visible wiggle or a thunk.

What does uneven cutless bearing wear mean?

Misalignment. Practical Sailor notes that wear on top at one end of the bearing and on the bottom at the other points to significant shaft misalignment. Check the engine mounts and the alignment, or the new bearing wears the same way.

How long does a cutless bearing last?

Good Old Boat says a properly aligned cutless bearing should last for several thousand hours. Misalignment, a bent shaft and running in silty water shorten that.

Is it cutless or cutlass bearing?

Cutless, as Practical Sailor's article title points out. Both spellings are searched for and mean the same part.

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