Centaur Cutless Bearing Removal and Replacement

From Westerly Wiki
Jump to: navigation, search

^Back

The Centaur Cutless Bearing is conveniently contained in a removeable bronze housing. To remove the housing it is necessary to remove the propeller.

NB Removal of the rudder is optional for this job but it is easy to do on lift out and makes for better access also if there is a rope cutter fitted behind the propeller it must be removed.

Start by removing the locking split pin from the castellated nut on the end of the prop shaft and unscrew the nut but do not take it fully off. The propeller is held tightly on a taper at the end of the prop shaft and must be persuaded to release from the taper. If a three legged puller is available (approx 4.5inches minimum span) mount this on the propeller with the pulling legs engaged behind the propeller boss. The pulling screw should rest against the end of the prop shaft just sitting in the castellation of the nut.

Tip: Whilst setting up the puller it helps to hold the legs of the puller together using a long cable tie.

Puller with cable tie

Wind the puller up hard making sure the legs remain engaged. then wait whilst adding release oil behind the propeller. Ideally the propellor will release from the taper but.....assuming nothing happens there are then two strategies that can be applied. These are heat and impact.

Removing the Propeller Using Heat

With the propeller under tension from the puller get a kettle of hot water and pour it over the propeller boss and again wait. There should be a bang as the propeller releases from the taper and springs back against the castellated nut which is still on the shaft to stop the propeller falling on your toes.

Removing the Propeller Using Impact

The second strategy involves two people and three club hammers used to strike the propeller boss in a "controlled" manner. First remove the puller if fitted but leave the castellated nut in place on the end of the shaft. One (large) hammer is used to support the propeller boss from underneath whilst the top of the propeller is struck from above. At the same time the second person strikes the back of the propeller (in line with the keyway if possible) towards the end of the shaft. The two hammer blows should be as near simultaneous as possible. As before there should be a bang and the prop should release from the taper but be prevented from falling off by the castellated nut.

Unscrew the castellated nut and remove the propeller. Remove the taper key from the shaft and store safely.

Prop Removed

Removing the Cutless Bearing Housing

Remove the top and bottom cutless bearing housing retaining bolts. They may have the nuts inside or outside and if on the inside the nuts may be glassed in. Access inside the hull to the lower nut may be difficult but a 14mm socket on an extension can be used to stop it turning.The socket extension passes under the stern tube to fit onto the lower cutless bearing housing nut hidden below the stern tube.

Access to lower nut can be difficult

Once the bolts are removed the cutless housing can be unscrewed anticlockwise from the stern tube using a large adjustable spanner.

Unscrew housing anti-clockwise

Removing the Cutless Bearing from its Housing

The cutless bearing is in a brass tube with bearing surfaces in the form of longitudinal water lubricated bearing strips. The brass tube is a tight press fit into the cutless bearing housing.

NB There are also two set screw that go through the side of the housing into the brass tube to stop the tube from rotating in the housing. These set screws must be located and unscrewed before attempting to remove the bearing.

Removal of the old bearing and replacement with a new one is most easily done in a workshop equipped with a press. Some vendors of cutless bearings offer this service. Alternatively the web documents diy removal techniques involving carefully sawing through the brass tube and collapsing the tube inwards to allow it to be removed using grips.

NB If a rope cutter fixed part (e.g. Stripper) is fixed to the cutless bearing housing it may be necessary to remove this in case the fixing bolts penetrate right into the brass tube.

Fitting the new Cutless Bearing

Replacement of the cutless bearing is the reverse of the above removal steps except that Sikaflex 291 should be used to seal the housing against the hull. The length of the housing bolts may differ and if it does the longer bolt is probably the upper one that has an extra nut and washer to secure bonding tags from the anode. On the inside of the hull there is a clamping plate that must be relocated.

clamp plate

Resources

Cutless Bearing supply and fitting here:

T Norris Marine Isleworth

Trafalgar Yacht Services

References

Propeller Shaft Upgrade for Westerly Centaur. Paul Shave Pg 53 Westerly Owners Association Magazine Spring 2008 Available here in WOA Members Technical Section

How to replace a cutless bearing. Rod Laws Page 77 Practical Boat Owner No535 June 2011

^Back