How to replace a cutlass bearing
Replacing a cutlass bearing is a haul-out job. The propeller comes off, the old bearing is pulled, pressed or cut out of its housing, and the new one is fitted, secured and checked. This guide sets out each step, the tools involved and the checks that help a new bearing last.
It is written for owners doing the work themselves and for owners who want to understand what a yard is quoting for. If you have not yet confirmed that the bearing is worn, start with the symptoms of a worn cutlass bearing.
Before you book the haul-out
Order the replacement before the boat is slipped, so the job is not held up waiting for a part. Each product page shows whether that bearing is in Australian stock. Sizes marked for pre-order have an estimated dispatch window of 3 to 4 weeks.
To identify the bearing you need the nominal shaft diameter, the housing bore and the bearing length, plus the shell material. The measuring guide explains how to take and record them, and the size chart lists every size we carry.
While the old bearing is still in place it hides the housing bore. A reliable drawing, the previous invoice or a code printed on the old bearing will usually identify it. Plan to confirm the bore once the old bearing is out and before the new one goes in.
Cutlass bearing removal tools
Most of the tools are standard workshop items. The one specialised tool is a bearing puller, and you may not need it if the shaft is coming out and you have access to a press.
- Propeller puller sized for your propeller, a socket or spanner for the propeller nut, and a new split pin or tab washer for reassembly.
- Allen keys or a screwdriver to suit the set screws that hold the bearing in its housing.
- Cutlass bearing puller. A length of threaded rod with nuts and washers, a plate that bears on one end of the old bearing, and a sleeve slightly larger than the bearing that sits against the housing at the other end. Tightening the nut draws the bearing out into the sleeve.
- Hacksaw blade in a pad-saw handle, for cutting through the shell of a bearing that will not pull.
- A press, or a hammer and drift. The drift is a bar or tube close to the shell's outside diameter, for driving a bearing out once the shaft has been removed.
- Measuring tools: vernier or digital calipers, a telescopic or bore gauge for the housing, an outside micrometer for the shaft, and a set of feeler gauges.
- Clean-up tools: a scraper and fine abrasive cloth to clean the housing bore without enlarging it.
- Safety gear: eye protection, gloves, and a dust mask for cutting or sanding phenolic and GRP.
Shaft in or shaft out?
Many strut bearings can be changed with the shaft left in place. Taking the shaft out is more work, but it lets you inspect the whole shaft and press the old bearing out in a straight line. Which approach suits your boat depends on the installation. On some boats the rudder has to be dropped before the shaft can slide out.
| Removal method | When it suits | Watch for |
|---|---|---|
| Bearing puller, shaft in place | Strut or P-bracket bearings with room for the puller sleeve, where the shaft does not need to come out for other work | Keeping the puller square so the bearing comes out straight; the shaft can only be inspected where it is exposed |
| Press or drift, shaft removed | Stern tube bearings, or jobs where the shaft also needs inspection or repair | Supporting the housing so it takes no load, and pushing on the shell rather than the rubber |
| Cutting the shell | A bearing that will not move with a puller or press | Cutting only through the shell, never into the housing bore |
Step-by-step: replacing a cutlass bearing
These steps are for Exalto sleeve bearings with a phenolic, brass or GRP shell. All-rubber bearings have no rigid shell and mount differently, so follow Exalto's installation instructions for those.
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Make the boat safe to work under
The boat should be chocked or on stands as the yard requires, with nothing relying on a jack. Isolate the engine so nobody can start it while you work on the shaft. Wear eye protection when cutting, drilling or striking metal.
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Record how everything sits
Photograph the propeller, strut and stern tube before you start. Note the number and position of the set screws, and measure how far the shaft moves in the old bearing. These notes help with reassembly and give you a comparison at the next haul-out.
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Remove the propeller
Remove the locking device and the propeller nut, then use a propeller puller to free the propeller from the shaft taper. Hammering on the propeller or the shaft end can damage the blades, the taper or the shaft thread. Keep the key somewhere safe.
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Free the shaft if it is coming out
Release the shaft seal or stern gland as its maker's instructions describe, then unbolt the shaft coupling from the gearbox. Check that the rudder or anything else is clear of the shaft's path before sliding it aft.
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Remove the set screws
Find every set screw that holds the bearing in the strut or stern tube; antifouling or filler can hide them. Remove each one completely. A bearing will not move while any screw is still engaged with its shell.
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Take out the old bearing
With a puller, put the plate against the end of the bearing and the sleeve against the housing on the opposite side. Tighten the nut steadily so the bearing comes out straight. With the shaft out, support the housing and press or drive the bearing out with a drift that bears on the shell.
If the bearing will not move, cut lengthwise through the shell with a hacksaw blade at one or two points, working from inside the bore. Stop as soon as the blade is through the shell, because a cut in the housing bore spoils the fit of the new bearing. Collapse the cut section inwards and the rest of the bearing should then come out.
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Clean and measure the housing
Remove corrosion, old sealant and marine growth from the bore. Use fine abrasive to clean the surface, not to enlarge it. Measure the bore at both ends and in two directions at right angles; the measuring guide explains why those readings should be kept rather than averaged. Check the strut for cracks and make sure its mounting is tight.
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Inspect the shaft
Look at the section that ran in the bearing for grooves, pitting or wear, and compare its diameter with an unworn part of the shaft. If the shaft is out, a machine shop can check its straightness. A worn or bent shaft shortens the life of a new bearing, so repair it while you have access.
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Check the new bearing before fitting
Compare the new bearing with the old one and with your housing measurements: shaft size, outside diameter, length and shell material. The bearing is made to be a light interference fit in its specified housing bore. If the bore is oversize, oval or damaged, deal with the housing before fitting.
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Fit the new bearing
Start the bearing squarely in the bore and draw it in with the puller, or press it in. Push on the shell end, never on the rubber lining. Keep petroleum grease and oil off the bearing and shaft, because they interfere with the water that lubricates the rubber, and use only the fitting lubricant given in Exalto's installation instructions. Position the new bearing where the old one sat, with the water grooves open at both ends.
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Secure it with the set screws
Line up the set screw holes with the new bearing. Where the housing uses set screws, spot-drill a shallow seat in the new shell under each hole so the screw locates in the shell. Never drill through the shell: a screw or drill point that reaches the rubber pushes the lining against the shaft. Replace corroded screws, and check that none protrudes into the bore.
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Refit the shaft and check alignment
Slide the shaft back through the new bearing, reconnect the coupling and reset the shaft seal. Check engine alignment at the coupling with feeler gauges against the engine maker's figures. Misalignment loads one side of the bearing and wears it unevenly. Many yards check alignment again after relaunch, once the hull has settled in the water.
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Refit the propeller
Clean the shaft taper and the propeller bore, refit the key and propeller, tighten the nut and fit a new locking device. Turn the shaft by hand: it should rotate smoothly with no tight spots.
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Relaunch and test
Check the shaft seal or stern gland for leaks as soon as the boat is back in the water. Run the engine in gear while tied up, then on a sea trial listen for noise and feel for vibration through the range of engine speeds. Note the date and your clearance readings for the next inspection.
Checking clearance on the new bearing
A new cutlass bearing is not a tight fit on the shaft. Its bore is made larger than the nominal shaft size to leave running clearance for the water film, so some movement is normal. Each product page lists that bearing's bore tolerance, and Exalto's tolerances and clearances give the design figures. Measure with feeler gauges at both ends of the new bearing and keep the readings as your baseline for judging wear later. The clearance section of our what-is guide shows worked examples.
How long does cutlass bearing replacement take?
There is no standard time. Fitting the new bearing is usually the quick part; most of the time goes on access and removal. These factors decide how long the boat is out of the water:
- whether the shaft can stay in place, or the coupling, shaft seal and rudder have to come apart;
- whether the old bearing pulls out or has to be cut out;
- repairs found during inspection, such as a worn shaft, a damaged housing or a loose strut;
- alignment checks, including any recheck after relaunch;
- the yard's slipping schedule, and whether the bearing is already on hand.
Ask the yard how long they expect the boat to be out, and have the new bearing delivered before the boat is slipped.
What does a cutlass bearing replacement cost?
The table shows what the Exalto bearings in our catalogue cost today, including GST. The other costs depend on your boat and your yard, so ask for them to be itemised.
| Cost item | Price guide (AUD) |
|---|---|
| Exalto phenolic cutlass bearing | $150.00 to $1,300.00 inc GST, across 81 sizes available online |
| Exalto rubber cutlass bearing | $115.00 to $150.00 inc GST, across 9 sizes available online |
| Exalto brass cutlass bearing | $175.00 to $2,395.00 inc GST, across 49 sizes available online |
| Exalto GRP cutlass bearing | $160.00 to $1,430.00 inc GST, across 75 sizes available online |
| Delivery within Australia | Free Australia Post Express Post |
| Haul-out, slipping and hardstand | Quoted by your yard |
| Labour to remove and fit the bearing | Quoted by your yard; depends on access and how the old bearing comes out |
| Shaft, strut or housing repairs | Only needed if inspection finds damage; quoted separately |
Bearing prices in this table are read from the catalogue whenever the page loads, using bearings that can be ordered online now. Sizes that need a quote are not included.
Related guides
A rudder bearing in a skeg is part of the steering and follows the boatbuilder's procedure rather than these steps; see the skeg bearing guide. If an old part is marked Johnson Cutless, cutless vs cutlass lists what to compare before ordering a different brand.