Cutless Bearing is loose in its housing - how do I re-bed it?

[npf1]

There's around a 1mm, maybe less, of play between my cutless bearing and it's housing (sterntube). Can someone please explain the prodecure to re-bed it? What exactly should I use Hylomar, Epoxy, Araldite etc? Do I need to /how do I ensure it aligned properly when it goes back in - shims?

Thanks in advance for your help.

BTW: I will be replacing the cutlass bearing itself, as it has some wear. Its bronze shelled, 1.5" internal diameter and about 6"long. Not sure about the outer diameter yet, until I get it out. Who sells replacements in the Swanwick area?

Nigel

 

[Topcat47]

Marine Power might be able to help with the cutless bearing, they are in Deacons yard at Bursledon Bridge, if My memory is correct..

If there's that much play in the housing, it'll have to come off. Without looking at it, I can't say whether it'll need replaced or whether you'll get away with skimming it. Then the steel sleeve of the cutless bearing can be turned down to size. It should be a slight interference fit.

The bearing is usually located by a grub screw.

 

[Tranona]

You do not say what material it is. It should be bored to take a standard size bearing. you will not be able to take up that amount of play as the bearing should be an inteference fit and located by a grub screw through the housing. If the housing is non standard then it will need boring out and sleeving back to the correct size.

 

[Talulah]

Sounds like the last time the cutlass bearing was replaced it was replaced with an imperial one into a metric housing or vice versa.
I suggest you measure the inside diameter of the housing with calipers and then order the correct one.
Some chandlers carry a small stock of cutlass bearings. I occasionaly see them for sale but personally have ordered from asap supplies.

 

[npf1]

I suspect the loose fit is due to the bearing spinning in the stern tube rather than being replaced with the wrong size. I'm also reasonably sure that it is a standard size rather than a custom one.

I had a boatyard replace the cutless when I first got the boat and there was no movement when it had been done. At that point, I knew sweet FA about these things and didn't check it before it was launched. At the next haulout, one of the set screws was missing whilst the remaining one was loose and not in line with the dimple on the outer shell of the bearing.

The stern tube is fibreglass and comes through the back edge of the keel - this is on a long keeler.

Skimming - Not sure I understand why you suggest that.

I read some old posts that mention bedding on epoxy, or Araldite. Do I need to worry about alignment?

 

[charles_reed]

[ QUOTE ]
Marine Power might be able to help with the cutless bearing, they are in Deacons yard at Bursledon Bridge, if My memory is correct..

If there's that much play in the housing, it'll have to come off. Without looking at it, I can't say whether it'll need replaced or whether you'll get away with skimming it. Then the steel sleeve of the cutless bearing can be turned down to size. It should be a slight interference fit.

The bearing is usually located by a grub screw.

[/ QUOTE ]

First time I've heard of a steel sleeve to a cutless. They're usually bronze or phenolic.

The OP sounds as though his boat was fitted with a wrong OD bearing - I'd suggest a careful use of vernier calliper to get the correct dimensions - suppliers Lake Engineering or (manufacturers) or c
Countrose.

 

[wotayottie]

[ QUOTE ]

The stern tube is fibreglass and comes through the back edge of the keel - this is on a long keeler.




[/ QUOTE ]

Aha! I had the same problem plus in my case the bearing was non standard. Norris made me a bearing to fit (not cheap but well done) and since the stern tube was slightly oval I bedded the bearing on silicone. I may yet regret that if it comes to needing a bearing change, but it has worked for now.

Alignment? Dont worry - its effectively self aligning on assembly.

 

[Cliveshep]

What the OP means by skimming is boring out the housing even larger to permit the fitting of a tube inside it the bore of which is the same plus a thou or so as the new bearing. In other words, an engineer's way of reducing the 1mm or so slack you have. I'm afraid no other way short of replacing the 'P' bracket is going to solve that one from what you are saying. The cutlass bearing has rotated inside the housing and worn it away so that any new bearing will also rotate. Chances are the actual wearing surface of your bearing has hardly worn at all, it is the outside that has worn along with your housing.

 

[TigaWave]

Firstly we supply cutless bearings to any size, as they can be machined to a finsihed OD or left for finishing on site.

Bearings can and are, frequently fitted as a clearance fit in the carrier bedded on epoxy. We recomend Araldite 2001 also known as precision. The reason is, it is a low melting point epoxy to aid removal. You can thicken it with talkum powder to help in fitting.

For grp stern tubes you can apply a wax release agent to the bearing, it can then be split from the grp tube for removal.

With regards to alignment, with the shaft supported the bearing should be able to be spun on the shaft and in the carrier, this confirms carrier alignment with shaft. You can then epoxy the bearing in the carrier with the shaft supported until the epoxy sets.

If you want to know what sort of clearance to leave on shaft and carrier you can use this calculator.
Bearing clearance calculator

This is what we recomend and may not be the same for other makes of bearing.

Other bearings may also be fitted bedded on epoxy rather than being an interference fit, but you need to talk to the bearing supplier as to what they recomend with regards size and fixings.

 

[Bilgediver]

......try not to get them worried.....We might be used to 1MM clearance on 525MM however here folk recomend more than 1 mm on 25mm LoL

 

[TigaWave]

(you have to put in the shaft and carrier dimensions you are looking at, it's a calculator)
shaft 25.40 carrier 38.10 (1"x1.5")
You get
ID max = 25.66
OD Min = 37.85 (clearance fit bedded on epoxy)

We can do the 525.00mm shaft if you like though.

 

[npf1]

Thanks for all the replies. Those that cover some of the orginal question asked seem to indicate a) use epoxy for bedding in the new cutless, which should be covered in a release wax, and 2) there's no need to worry about alignment. Is my understanding correct?

 

[TigaWave]

You can bed on epoxy, but check with the bearing manufacturer, we advise wax release with composite bearings in GRP carriers.

You always need to make sure engine and shaft are aligned. What the bedding on epoxy helps with is that it allows you to confirm that the carrier is in alignment with the shaft line. it's not there to take up misalignment.

But to be honest on a small shaft of low power the issues with regards to wear/vibration/noise are small when compared to several thousand hp and 15' shafts.

 

[wotayottie]

[ QUOTE ]
Thanks for all the replies. Those that cover some of the orginal question asked seem to indicate a) use epoxy for bedding in the new cutless, which should be covered in a release wax, and 2) there's no need to worry about alignment. Is my understanding correct?

[/ QUOTE ]

With a grp tube I wouldnt go near epoxy. You would never seperate it from the tube itself and it could so easily grip the bearing in places like the indents for the screws.

As someone has pointed out, the ideal solution would be to ream out the stern tube and then epoxy into it a fixed brass liner tube which subsequently would take the bearing assembly. But in my case and maybe yours, the grp tube is not that thick walled that I would feel comfortable making it thinner by reaming.

Truth is that a grp stern tube is a b silly idea.

 

[TigaWave]

Composite cutless bearings are routinely bedded on epoxy with a release agent/wax in GRP tubes and have been for at least the last ten years. Not a great photo but you can see one here on a new build 48.00mm shaft.

 

[wotayottie]

so how do you avoid the epoxy gripping in the dimples that have to be there for the grub screws - let alone any machining marks on the outside surface.

 

[Neil_Y]

You don't need grub screws with epoxy, and a sharp chisel will seperate the old bearing for removal. Look at the photograph above, this is on a production boat that has used this technique for many years.