Cuttless Bearings and Grub screws

[xeitosaphil]

Boats out at the moment as I want to re -align the engine.

One small question, I have always fitted Phenol Cutlass bearings in the past as they are easy to replace and that was what was used when I did my first one, but now wonder about fitting a brass shell bearing instead? The reason being is that I only have one grub screw to fix it in place, and I thought that I might get a better security with the screw actually tightened up against the Brass shell?

I have wondered though, is this normal just to have one screw in the stern tube, I would have though it would have been two?

The only good thing about the Phenol Bearing is, it does swell to the inside dia of the stern tube which could provide an equally secure compression fit, where as the brass shell will only be as good as the grub screw provides.

In a bit of a quandary as which would be better suited?

Oh and one other question, does anybody have any experience of a Yanmar 2GM20 dancing fore and aft at different revs? I know they are prone to considerable vibration at low revs sideways but mine seems to dance up and down, fore and aft.

Feet are relatively new 5 years old R&D super mounts which work really well.

Any ideas what could be causing the engine dance?

As always thank for any replies,

Philip

 

[Tranona]

Why not change to a composite bearing which is epoxied into place and does not rely on the grub screw. H4 Marine will make one for you. BTW the grub screw only does anything if the bearing is not a press fit in the housing. Usually the problem is removing the bearing rather than it moving on its own.

 

[Ruffles]

Brass one should be a reasonably snug fit.

But most people carefully centre punch the brass through the grub screw hole and drill a dip.

Antifoul stops the grub screw falling out!

PS: Ours has two hex SS grub screws with what looks like a whitlock thread. One is somewhat knackered so I have a dedicated alum key for removing it.

 

[Sailfree]

Why not change to a composite bearing which is epoxied into place and does not rely on the grub screw. .

How do you replace an epoxied in cutlass bearing?

 

[alahol2]

How do you replace an epoxied in cutlass bearing?

Warm it up and the epoxy melts.

 

[xeitosaphil]

Brass one should be a reasonably snug fit.

But most people carefully centre punch the brass through the grub screw hole and drill a dip.

Antifoul stops the grub screw falling out!

PS: Ours has two hex SS grub screws with what looks like a whitlock thread. One is somewhat knackered so I have a dedicated alum key for removing it.

Rob, if yours is a snug fit and not a press/ force fit ( which I assume means the bearing is somewhat oversized of the stern tube and needs pressure/force to insert it), do you have any problems removing yours as Tranona suggests some people do?

Are there any tips necessary when removing your brass shell bearing , or is it just a matter of unscrewing the grub screw and out it comes.

I'm hopeful if I use a brass shell type that I won't be needing to cut it out like I do with the Phenol one. I was wondering what problems people have removing these type of bearings from stern tubes, as I have heard about difficulties before, but can't remember the details or the reasons behind them.

Philip

 

[Tranona]

Depends entirely on how tight a fit it is rather than the material. If the bearing is a press fit then you will need a press or an extractor to remove it. Alternative is to cut it out.

 

[xeitosaphil]

Depends entirely on how tight a fit it is rather than the material. If the bearing is a press fit then you will need a press or an extractor to remove it. Alternative is to cut it out.

Thanks Tranona for your input, I think I will have to get a brass shell one and try it in the stern tube. If it needs some force to put it in I may go back to using a Phenol one only I don't fancy having to cut a bass one out!

Not sure what type of extractor you mean, but a the bearing would be fitted right uptight to the stern tube shoulder. So there would not be any room behind it to get a puller with arms behind it, if that was the type you were suggesting?

Phil

 

[Tranona]

Depends on what the housing is. If it is in a P bracket, then an extractor would take the form of a disc on a threaded bar wher e the disc is small enough to go through the housing . Similar arrangement if the housing is detachable from the stern tube, although in this case easier to put it in a press. If the bearing goes into a housing that is part of the hull, then these methods will not work.

 

[xeitosaphil]

Depends on what the housing is. If it is in a P bracket, then an extractor would take the form of a disc on a threaded bar wher e the disc is small enough to go through the housing . Similar arrangement if the housing is detachable from the stern tube, although in this case easier to put it in a press. If the bearing goes into a housing that is part of the hull, then these methods will not work.

Mine is the last situation where the bearing goes into the stern tube which is fitted flush with the outside of the keel edge, so I take it the only way is to cut it out, unless anybody knows of a suitable extractor / puller?

Philip

 

[Tranona]

You could feed a threaded bar with a disc on the end the same diameter as the bearing. A tube over the outer end of the bar that clears to outside of the bearing and bears on the hull, plate on the end with nut to wind the bar out, pulling the bearing with it.

Just a bad bit of design hiding the bearing in a tube like that with no thought given to easy replacement and having to rely on a grub screw for location. Compact, though and commonly used particularly when there is a need to minimise the size of cut out for the prop.

 

[wrr]

If the bearing carrier is mounted on the deadwood, with only the aft end accessible, then it may be easier to use a brass shelled cutless bearing and leave 10mm or so proud of the bearing carrier. This will enable purchase on the cutless bearing for either a large water pump pliers or Stillson, or in extremis, for a small cold chisel with which to drive the bearing out. The brass bearing shell should be able to resist any deformation in the protruding part during use with a small diesel. This allows removal of the bearing without having to draw the shaft or remove the bearing carrier. Alternatively, as stated above, you can use a composite bearing and epoxy it in. It should be possible to work it out of a heated bearing carrier as long as you do not burn the deadwood.

 

[Len Ingalls]

http://downeasteryachts.com/info-index/engine/cutlass-bearing-replacement

 

[xeitosaphil]

Thanks for the link, but unfortunately my stern tube isn't like that. It doesn't have a outside flange carrier, the stern tube cutlass carier finishes flush with the back side of the keel.