REPLACING CUTLESS BEARING (part two)
avatar

When removing the cutless bearing, corrosion was discovered on the propeller shaft. During the winter I contacted VETUS in Athens.  They provides excellent service and delivered a new shaft in Duplex steel to Leros.

In March I spent a week in Leros installing the new shaft, and doing some other maintenance work.

The new cutless bearing was glued in place with epoxy.  In addition 2 set screws secures the bearing in the GRP tube.

New bearing sticking out 20 mm from the tube.

New bearing sticking out 20 mm from the tube.

Then it was just to fair the area around the cutlass bearing with a filler.

Cutlass bearing installed

Cutless bearing installed

Back in the engine room it was obvious that the shaft was not centred in the stern tube.  I realized I had not checked this when removing the old shaft.  But after looking on the wear in the shaft seal it was obvious that the shaft had been sitting low for a long period.

Shaft touching the tube

Shaft touching the tube

The fact that the shaft is not centered in the shaft tube does not necessarily  mean that the engine has been misaligned.  It is possible to align the engine perfectly even when the shaft is not centered.

A proper alignment includes two steps.

1. Center the shaft in the shaft tube. This is done to make sure that the shaft does not touch the tube when motoring. When centered there is about 5 mm clearance on each side of the shaft.  Normally you use 4 wedges in order to center the shaft.  Another easier way is if you manufacture a tool that fits in the propeller tube with a hole for the shaft.

2. Next step is to align the engine to the shaft when it is centered in the tube.   Make sure that shaft is centered in the tube with the help of 4 wedges or the tool. Then it is time to adjust the height of the engine.  You have to adjust the engine until it is aligned vertically and horizontally. Then you have to make sure that the shaft coupling is parallel  with the gearbox.

Realigning the engine is something that requires skill and proper tools.  I had the intention to do this myself, but soon realized I did not have the proper tools.  I asked Nikkos on Artemis Boat Yard if he knew anyone that could help.  A local mechanic, Chris, came down and discovered that shaft was off-center and the engine misaligned.

Chris declaring , job is done!

Chris declaring , job is done!

Even with the misalignment the engine has run smooth. That just show how efficient a Centaflex  take up misalignment.  Or perhaps is it a proof that alignment is not that sensitive?  I did find this interesting article about free floating semi self-aligning system.

Centaflex CF-M 160

Centaflex CF-M 160

When loosening the bolts that holds the flexible mounts, all came loose but one.  The one that was stuck, was the one under the water pump.  Water from the pump had dripped down in the thread and caused corrosion.  Heavy tools were needed to loosen those bolts.

After 2 hours Chris said, “now it is perfect”.

This all started as a “simple” job. Without complications it would have been a 3 hours job.  But as always surprises showed up:

1. Shaft needed to be changed due to crevice corrosion.

2. Shaft not centre which meant alignment required.

3. One bolt holding the flexible mount was frozen in the thread.

Dealing with complications are much easier if you have time and are in a place with good infrastructure. This is why I prefer to schedule this type of work when the boat goes in to storage.

If you missed part one “How to replace cutless bearing. Click here.

 

 

 

 


Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.