Oversized Cutless bearing problem

[Jcorstorphine]

I have just removed the original rubber cutless bearing from a Stuart stern tube.

The one I removed was 100 % rubber being 1.875” OD by 1.000” ID. (well it was when it was new)

These are no longer available but I have a replacement which has a Phenolic shell of the same OD and supposedly a rubber insert with an internal diameter of 1.000”

The shell is 0.300” thick so is much greater than the conventional Phenolic shell bearings.

My concern is that the shaft which is bang on 1.000” +/- a thou is like a sausage in a shirt sleeve with about 40 thou movement. It is actually worse than the one I removed.

I have been told that once the boat is in the water the Phenolic sleeve will expand inwards thus gripping the shaft.

I am not convinced. Anyone have experience of these types of bearings?

 

[Ammonite]

I have just removed the original rubber cutless bearing from a Stuart stern tube.

The one I removed was 100 % rubber being 1.875” OD by 1.000” ID. (well it was when it was new)

These are no longer available but I have a replacement which has a Phenolic shell of the same OD and supposedly a rubber insert with an internal diameter of 1.000”

The shell is 0.300” thick so is much greater than the conventional Phenolic shell bearings.

My concern is that the shaft which is bang on 1.000” +/- a thou is like a sausage in a shirt sleeve with about 40 thou movement. It is actually worse than the one I removed.

I have been told that once the boat is in the water the Phenolic sleeve will expand inwards thus gripping the shaft.

I am not convinced. Anyone have experience of these types of bearings?

Log on to the ASAP supplies site. The new fibreglass range of cut less bearings are the way to go. The phenolic one I fitted previously did not swell as promised

 

[Neil_Y]

For a carrier ID of 1.875" (47.625mm) shaft 25.40
We would supply a bearing of ID (25.58-25.68) x OD (47.33-47.43) x whatever length you wanted.
Clearances come from the allowances below.
Min Running 0.03mm
Moisture closure 0.06
Thermal closure 0.09
If a manufacturer is telling you a shell will experience bore closure from moisture they need to tell you how much, but thermal swell will be far greater.

 

[vyv_cox]

I have been told that once the boat is in the water the Phenolic sleeve will expand inwards thus gripping the shaft.

I am not convinced. Anyone have experience of these types of bearings?

That is my experience. I fitted a phenolic sleeve type a long time ago and rang the supplier with my concerns that the shaft was rattling inside it. I was told the same as you have been, and the advice turned out to be correct. However, checking on the next haul-out the shaft was very tight in the bearing, which leads me to suppose that the swell may be somewhat unpredictable. That's the one and only phenolic sleeve I have ever fitted, brass only from then on.

 

[Tranona]

Think the rubber bearing is still available from Lake Engineering. Alternative is to sleeve the ST housing to take a brass shell cutless. Another possibility is. New housing to take a cutless from I think French Motors.