changing cutlass bearing

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chrisb

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need to replace the cutlass bearing on my prop shaft.guess this means removing the blades from my 3 bladded volvo folding prop to access the prop hub and then removing .extract the old bearing and reassemble.yard quotes 3.5 hrs labour ie £175.is this a difficult job or one i can easilly do myself?seems a little steep
 
The prop to come off, the shaft may have to be dropped back a few inches to allow the bearing surface of the shaft to be measured accurately, the old bearing has to be removed, (which is OK if you have a removeable bearing housing as it can be done on the bench). The new bearing has to be sized to the shaft, usually on a lathe, sometimes having to be cut to fit the housing (also best done on a lathe). It then has to be reassembled. 3.5hours seems about right to me, allowing for some contingency (ever tried removing the wheel bearings on an old car?). You could save a bit by removing and replacing the prop yourself, and even the cutless bearing housing, but cutting and fitting the bearing is best left to the professional.
 
It really depends how much time you have spare as to whether this is a good price. If you have loads of time, you could charge yourself out at £10 per hour and take up to 17.5 hours to do it at no extra cost. If no time then you'll have to pay. Please don't interpret this as a facetious response, it is offered with good intent.
Out of interest, does their quote include the new bearing or not?
Nicki
 
Why do you need to replace the bearing? They normally last for hundreds of hours running. The bearing is fluted rubber and the shaft should be loose in the bearing to avoid overheating.

If you have to change the following web site is good.

http://www.diybob.com/diyCutlessBearing.htm

With Beneteaus the cutlass bearing is normally a loose fit in the P bracket and held in place with 2 stainless grub screws. Take the prop off, remove the grub screws and the bearing should slide out of the p bracket and down the prop shaft
 
So £225. I'm with Hunter on this; best do it yourself if you can. It really in not that hard. If you're unsure, buy Nigel Calder's bible 'Boat owner's mechanical and electrical manual'. Can't really go wrong.
Nicki
 
So £225. I'm with Hunter on this; they last for ages, but if it does need replacing, best do it yourself if you can. It's really in not that hard. If you're unsure, buy Nigel Calder's bible 'Boat owner's mechanical and electrical manual'. Can't really go wrong.
Nicki
 
The cutless bearing should be a push fit into the housing, located by one or two grubscrews. These are to prevent the bearing turning in its housing. The shaft should turn in the bearing but if you can feel side to side play, it's worn.

"P" brackets are easily got at, but a combination of fouling and corrosion can make the grub screws AND the bearing B@%%&*£ to remove. The grub screws can be drilled out, the holes re-tapped and bigger screws fitted if necessary, but the bearing may need to be drifted out.
 
If it is not vibrating or doing anything else you would wish it not to, I'd leave it.
Can anyone explain how vertical and not lateral movement appears?
Nicki
 
Is that free movement ie clearance in the bearing or the ammount it flexes when pushed?

3 mm of clearance is normally the time to change. Strange the wear is only vertically.
 
This is not in a P bracket, but in a stainless steel tube, held in place by a grub screw. It needs an extractor as the tube is bonded into the hull. The shaft will also need to be withdrawn to use the extractor.
The movement you have suggests replacement is needed, otherwise the shaft may wear (even if you have no noise/vibration) and then you are into much bigger bucks. The hours and price sound about right, and unless you are confident about your ability to extract the cutless, the only saving would be you doing the removal of the prop. Probably best to pay the yard.
 
Can anyone explain how vertical and not lateral movement appears?
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This suggests to me that the engine is slightly out of alignment and trying to either lift or depress the shaft so putting a load on one side only of the cutless bearing.

This could be due to the mounts at one end of the engine going soft or something else.

This would cause the shaft to sit firmly in one position and only move in one direction either up or down when you apply pressure to the prop IE not lie centrally.

The danger here is that only one side of the bearing is being worn!!

In the event the bearing is changed then the engine alignment must be checked and corrected if necessary.

If the engine is realigned with the old bearing in place then vibration may be experienced as the shaft will be free to move vertically.. /forums/images/graemlins/ooo.gif
 
Vertical movement is due to the weight of the prop and shaft beraing downwards on the bearing when stationary. 3mm up and down is not excessive unless the diameter is very small and even then not a cause for immediate replacement if there is no vibration. Bearings are available off the shelf in the correct sizes and do not need turning or adjusting - if you buy the right one!!
Countrose are the main suppliers but I would leave it for this season.
 
Thanks. All is clear now. All my boat with inboards have been long keelers so it really is an easy job. I think I'll shut up now as I don't really have a clue what I am talking about. /forums/images/graemlins/smile.gif
Nicki
 
Chris, as Bilgediver has already said the most likely cause of the bearing wear presenting vertically with insignificant horizontal wear is mis-alignment.
3mm is excessive wear for a small shaft to cope with. You did not specify the shaft diameter and I am asuming that it is less than 2"
If the boat is still on the hard I think you should investigate further. High speed shafts such as propeller shafts are intended to ride on a film of water between bearing and shaft, not rub directly against a bearing and shaft wear will also result if the alignment fault is not remedied.
 
Vertical misalignment will do that. A flexible coupling will permit a little angular flexion, but if the shaft end of the coupling is a little below the gearbox flange....need I say more?
 
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