Beneteau cutlass bearing.

[Allan]

We have a Starlight 35 which has previously been converted to a Beneteau type cutlass bearing. We've been changing it approximately every two years due to wear. I'd like to know how they normally work on a Beneteau.
Ours has a hole (approximately 10mm) part way along the stern tube. I assume this is to let water in to cool/lubricant the bearing. Is this the same as a Beneteau? We have a Volvo seal at the other end of the stern tube. The prop feathers, so does not turn while sailing.
We sail a couple of thousand miles a year but use the engine minimally.
Allan

 

[Tranona]

Not sure why one would choose that type of bearing through chooice. There are much better bearings available. In Benetaus and Jeanneaus that use that there is usually forced water feed either through a scoop or from the engine cooling system. A conventional fluted cutlass type bearing is probably more suitable but of course it depends on your bearing housing. I would think you have aa 30mm shaft and cutless bearings are available in the same 30ID/40ID *120L size. With your type of usage and a properly aligned shaft they should last for many years. An alternative would be a custom made composite bearing

 

[vyv_cox]

The prop feathers, so does not turn while sailing.

Are you sure about this? Our Bruntons feathering prop always rotates when sailing unless we engage reverse gear. I don't know for certain about other makes but I recall reading that some behave as the Bruntons does.

 

[Amlov]

Most Starlight 35 boats have a 25mm shaft and 1 3/8” stern tube, which is almost 35mm and occasionally the metric versions have been squeezed in.

We have recently been through a period of rapid cutlass bearing wear, which wasn’t solved by engine alignment or having the prop balanced. We tried bearings from two different sources and in both cases there was noticeable wear after 100h and they need to be changed at two years. But having changed to a third type we have had no wear over the past three years.

So I do wonder if the issue is the type of bearing being used rather than anything more fundamental.

 

[Tranona]

It might be worth trying a composite bearing made to size from something like Vescanite or Maritex. H4 Marine in Devon offer these.

 

[Allan]

Most Starlight 35 boats have a 25mm shaft and 1 3/8” stern tube, which is almost 35mm and occasionally the metric versions have been squeezed in.

We have recently been through a period of rapid cutlass bearing wear, which wasn’t solved by engine alignment or having the prop balanced. We tried bearings from two different sources and in both cases there was noticeable wear after 100h and they need to be changed at two years. But having changed to a third type we have had no wear over the past three years.

So I do wonder if the issue is the type of bearing being used rather than anything more fundamental.

Many thanks,
The one I'm about to fit is in a box marked Exalto, British made, 25x36x100x46x5mm all rubber bearing. (MRSFF25x36x10). Do you know the manufacturer of your successful bearing?
We don't have the pumped feed mentioned above although I'm thinking of making some form of scoop to try to increase the flow.
The prop is a Darglow and once stopped by putting in reverse does not turn whether left in reverse or put back to neutral.
Allan

 

[Tranona]

If your tube is indeed 1 3/8" (34.9mm) then a 36mm OD bearing will compress as you force it in and reduce the ID clearance required for water circulation and wear out quickly in use. A custom made composite bearing is probably the way to go. It will be made to fit your stern tube and the correct ID for your shaft. The radical alternative is to change the shaft to an Imperial 1" and use a standard 1"*1 3/8" fluted cutless bearing. Not quite as dramatic as you might think as you could have your shaft coupling bored out to 1", a new shaft seal and a 1" shaft with a taper (probably 1:10) to fit your propeller. I did something similar converting from a 1 1/4" shaft to 30mm with a 25mm taper to fit the Darglow propeller. The work was done by Lake Engineering in Poole.

Edit. Thinking a bit more, you would not need to change coupling and seal if you had the 1" shaft turned down to 25mm as far as past the seal into the stern tube and then 1" through the cutless and a taper to match the propeller. Check though the exact ID of the tube as a shelled cutless bearing has to be an exact fit.

 

[ithet]

By "Beneteau type cutlass bearing" do you mean the type that is like a normal fluted bearing but with a flange at one end? I use the Exalto ones on my Beneteau. On Beneteaus these push into a moulded skeg where the tube exits the hull. Beneteau provide the forced water feed as standard at the top of the tube but as these are known to be a weak point I have had mine removed and sealed, then replaced the feed via one of the new stern seals that can take a water feed.

However, I am not convinced of the need for the forced water supply at all, because in the cases where the water feed connection has broken, reports are that water was entering the boat, suggesting that there is flow past the cutless bearing anyway.

 

[Amlov]

Many thanks,
The one I'm about to fit is in a box marked Exalto, British made, 25x36x100x46x5mm all rubber bearing. (MRSFF25x36x10). Do you know the manufacturer of your successful bearing?
We don't have the pumped feed mentioned above although I'm thinking of making some form of scoop to try to increase the flow.
The prop is a Darglow and once stopped by putting in reverse does not turn whether left in reverse or put back to neutral.
Allan

Yes the current one is Exalto MIBSF25-1 which was a special order.

When we bought the boat there was very little wear in the bearing (I suspect was from new) but as I had the shaft out and was changing a lot in the stern gear, I changed it for what was sold as an Exalto bearing. This barely lasted two years, I then changed it again for one supplied by C&O that was 25*35mm. This was too tight so they turned it down and I fitted it. Again it only lasted two years and Exalto confirmed that neither were their’s. Exalto have very good support if you give them a ring.

I spent a lot of time and effort trying to get to the bottom of my excessive wear before concluding it was the bearing - rather than my set up.

I am not sure why or how yours was converted to the flanged bearing, but I have seen some Starlights where the wrong sized bearing has been fitted and the glass stern tube damaged. However, I have never heard of one that doesn’t have the 1 3/8” stern tube so if you are fitting a 36mm bearing something is either wrong or modified.

If you want further details it might be best to DM or raise the same question on the Sadler Starlight Owners Facebook Group where there is a lot of expertise.

 

[Beneteau381]

Not sure why one would choose that type of bearing through chooice. There are much better bearings available. In Benetaus and Jeanneaus that use that there is usually forced water feed either through a scoop or from the engine cooling system. A conventional fluted cutlass type bearing is probably more suitable but of course it depends on your bearing housing. I would think you have aa 30mm shaft and cutless bearings are available in the same 30ID/40ID *120L size. With your type of usage and a properly aligned shaft they should last for many years. An alternative would be a custom made composite bearing

Cutless

 

[Beneteau381]

We have a Starlight 35 which has previously been converted to a Beneteau type cutlass bearing. We've been changing it approximately every two years due to wear. I'd like to know how they normally work on a Beneteau.
Ours has a hole (approximately 10mm) part way along the stern tube. I assume this is to let water in to cool/lubricant the bearing. Is this the same as a Beneteau? We have a Volvo seal at the other end of the stern tube. The prop feathers, so does not turn while sailing.
We sail a couple of thousand miles a year but use the engine minimally.
Allan

The cutless top hat bit needs to have gap between the prop/line cutter and the top hat for water to access the flutes and lube the bearing. IIRC it needs 15mm gap

 

[Allan]

Yes the current one is Exalto MIBSF25-1 which was a special order.

When we bought the boat there was very little wear in the bearing (I suspect was from new) but as I had the shaft out and was changing a lot in the stern gear, I changed it for what was sold as an Exalto bearing. This barely lasted two years, I then changed it again for one supplied by C&O that was 25*35mm. This was too tight so they turned it down and I fitted it. Again it only lasted two years and Exalto confirmed that neither were their’s. Exalto have very good support if you give them a ring.

I spent a lot of time and effort trying to get to the bottom of my excessive wear before concluding it was the bearing - rather than my set up.

I am not sure why or how yours was converted to the flanged bearing, but I have seen some Starlights where the wrong sized bearing has been fitted and the glass stern tube damaged. However, I have never heard of one that doesn’t have the 1 3/8” stern tube so if you are fitting a 36mm bearing something is either wrong or modified.

If you want further details it might be best to DM or raise the same question on the Sadler Starlight Owners Facebook Group where there is a lot of expertise.

I believe the end of the stern tube was machined to ensure it was the correct size for the Beneteau bearing.
Is your bearing brass?
Allan

 

[Allan]

The cutless top hat bit needs to have gap between the prop/line cutter and the top hat for water to access the flutes and lube the bearing. IIRC it needs 15mm gap

The gap is about 25mm.
Allan

 

[Amlov]

I believe the end of the stern tube was machined to ensure it was the correct size for the Beneteau bearing.
Is your bearing brass?
Allan

Yes, it is the standard brass shell cutless bearing - the only issue being that it is an unusual size (but standard for Starlight 35).

 

[Allan]

Yes, it is the standard brass shell cutless bearing - the only issue being that it is an unusual size (but standard for Starlight 35).

I've just spoken to Exalto, unfortunately as our stern tube has been machined that bearing won't fit correctly. It also has the same bearing material as the ones we've been using so would probably wear the same. Do you have a water feed from the engine or a supply hole along the stern tube?
I'm thinking of trying to increase the amount of water going into the stern tube by adding a scoop and/or increasing the hole size. Before I do I'm going to ensure the tube is not full of silt.
Allan

 

[Tranona]

The simplest way of getting waterflow is to replace the Volvo seal with a Radice version which has a direct water feed from the engine, as well as a greasing point. Photo shows mine, although I don't use the tube for water, just as a vent because my tube is very long and water flow is not an issue. The vent (or water feed) means you don't have to "burp" the seal when you launch and ensures the stern tube is always full of water.

 

[Amlov]

The simplest way of getting waterflow is to replace the Volvo seal with a Radice version which has a direct water feed from the engine, as well as a greasing point. Photo shows mine, although I don't use the tube for water, just as a vent because my tube is very long and water flow is not an issue. The vent (or water feed) means you don't have to "burp" the seal when you launch and ensures the stern tube is always full of water.

I think this is a very sensible suggestion, but I am not 100% convinced that waterflow is the problem. My understanding is that about a 6mm gap between the cutless bearing and the propellor boss is enough to develop a film for the shaft to run in within a 4” long bearing.

But I wonder whether some of the problems are due to the fact that the bearing is all rubber. The Starlight has quite a long shaft which is just on the limit that people quote for a 25mm shaft, which combined with quite a large prop (15-16”) puts stress on the cutless bearing and looses the film that the shaft runs in if the prop bounces around a bit (much like wear accelerates as clearance around the shaft increases). With the greater the rubber thickness the more this will compress and promote wear. So your earlier suggestion of a composite bearing is also worth further investigation, along with an intermediate bearing.

Then, there are obviously some questions about whether the tube was machined central and parallel. I am fairly sure the machining would have been done in situ to address damage. I have heard of one where an incorrect sized bearing was running in the stern tube (1999 model), but I doubt that the damage was central and repair might have been quite technical.

Although the OP has rapid wear it is unclear whether this is a new thing, or whether this has been a problem since he bought the boat/had the stern tube modified. These may have different solutions.

 

[Tranona]

Mine is a very different style of boat, but the engine/transmission is much the same The shaft is very long (54" from memory) and we had the same discussion when changing the engine The previous engine was a Perkins 35hp (down rated Volvo 2040) and the new is a Beta 30 with a PRM 2.5:1 box. Normally a 25mm is fine with a 30hp. but the combination of the length and a Featherstream 16" suggested there might be an issue with shaft whip. The inboard end of the tube had an old style stuffing box which was machined to take a length of cutless to provide an intermediate bearing and a Radice seal. I had done a similar thing with an earlier re-engine job and it had worked well. Also the 30mm shaft size meant we could use a Vetus Bullflex coupling. As the small hub Featherstream will only take a 25mm/1" shaft the diameter was stepped down with a radius and a 25mm metric taper machined to suit the prop. The outboard bearing housing was machined to take a standard 30*120 cutless. It all works very well with virtually no vibrations. As I mentioned earlier the machining was done by Lake Engineering who made the new shaft.

I am not a lover of floating shafts but appreciate it is not always possible to provide a bearing on the inboard end. Alignment and centring the shaft in the tube are critical to minimise movement and wear, particularly when the shaft is near its limit in length and diameter for the engine power.

Photos show the inboard bearing and the outboard end with propeller. The inboard was a tight fit but fortunately there is a thin wall 40mm shell available. The outboard uses the standard 45mm shell. I don't know what the inboard end of the Starlight stern tube is like, but there is a thinwall shell (34mm) available for 25mm ID. It is short (60mm) but plenty for an intermediate bearing.

 

[Beneteau381]

The gap is about 25mm.
Allan

My Beneteau also has a thru hull with a 10mm tube allowing access by sea water at the Volvo seal, I’ve never figured out which way it goes, up or down. Some have some exhaust water piped through it to flush down the shaft to the cutless