Cutlass Bearing Query

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alec

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Can you only use a Cutlass Bearing in a 'P' Bracket setup ?

After 12 year's of having white metal bearings - both very expensive and less people doing them, I found a maker and purchased a Cutlass bearing that fits my stern tube and shaft perfectly. The Cutlass bearing fits inside the stern tube at the prop end.

An engineer has told me that this is no good as there is not a forward stream of water to lubricate the bearing. I have an aperture at the prop end (long keeler), the other end of my stern tube has a conventional stern gland with packing and a greaser.

Any thoughts ?

Thanks in advance.
 
the engineer is correct
some stern bearings are made foe cutlass bearings , they have normally 2 scoops @ the fore end to allow water to be forced through the bearing.
you could change the stuffing box with a dripless seal ( volvo,pss, ect ) & inject cooling water through that.
i did this on my previous boat Co32
 
Expert comment this is not, but my cutlass bearing has been replaced once in 4 years, and doesn't have a thro' stream, nor could it. Still does the job - and it's a motorboat!.
 
If it's under water then it is self lubricating and will work perfectly well. The engineer is wrong, ive fitted hundreds over the years, and if they are wet then they work. What they dont like is people who run their engines up on dry land and then put it into gear, they melt.
 
the tube will still fill with water and thus lubricate the bearing,
it is debatable if it is needed to have some form of entry for the water forward of the bearing.
if the bearing wears to soon it is most likely to be due to engine or shaft miss-alignment.
 
There is no need for forced water circulation on a yacht as the only benefit would be to cool the bearing and in ths country the ambient temperature of the sea water means this is done well enough with just the surrounding water. You will see more yachts without forced circulation than with it.
 
Despite the posts to the contrary it is perfectly possible to have a cutless bearing in a standard tube.

In common with many other boats mine has has had a tube-mounted cutless bearing for the last 18 years with no ill-effects.

Theoreticians and H&E experts have traits in common.
 
we replace white metal with composite cutless bearings, we do advise that there should be a water flow for cooling and lubrication, but as others have said in UK ambient water temp and if it has replaced a white metal bearing so the wall thickness is slim then you will get awat with less water flow.
We have a calculator here that gives water flow rates for our bearings, just enter the carrier ID and shaft details.

Calculator
 
As a marine engineer and ex yacht surveyor, I have wondered this one my self. I would expect that any bearing would require a replenished flow of coolant and lubricant. However, in over a thousand yacht surveys, I saw many cutlass bearings in a housing on the end of the stern tube with no means of capturing water flow. Seems to me that so long as the bearing and stern tube are flooded, in normal conditions this is sufficient. My own boat is the same. Maybe the composition of the rubber is slightly different for these different conditions? Worth enquiring.
 
Wow ! What a fantastic response !

Enormous thanks to you all for the contributions.

It just proves what a great resource we have here to share thoughts and experiences.

As a matter of interest, the bearing I have was sourced from Aquafax in the UK which leans very much to supplying boaty things.

The outside diameter is 1.25 inches and the internal is 1 inch. The nitril is rather thin compared to others that I have seen but I suppose it has to be. The cost was 30 UK Pounds compared to 160 pounds for the last white metal bearing 7 years ago.

Once again, thanks for all the responses.
 
when i changed my Co32 from white metal to cutlass with the deep sea seal & water filtered through the vetus type strainer to lube the seal the shaft wear was greatly reduced.
we are east Coast based with loadsa sediment suspended in the water, it was supprising what sediment was trapped in the strainer
 
When the white metal bearing in my stern tube was replaced with a cutless bearing the engineer drilled two opposite 5mm holes in the external part of the stern tube to ensure the stern tube was flooded. This seems to work as three years have passed with no problems.
 
The engineer that said that a Cutless bearing could not replace a white metal bearing in a housing mounted on the end of the stern tube is talking b0ll0cks. That is the arrangement on Wight Dawn and, while I had to replace the Cutless last year after replacing it 8 years before, it was not the lack of lubrication that caused the problem.

To cut a long story short, when the white metal bearing was originally replaced (before I owned the boat) the hole in the housing was off-centre, and of too small a diameter. so the shell of a Cutless bearing was turned to fit. The bearing was off-line to the shaft and the stern-tube end was actually about to shear off at housing, which it did when the housing was being removed. Repair involved having a new housing cast (and PROPERLY machined to fit a standard Cutless bearing) and a new stern-tube. The new bearing could not be obtained from ASAP however as the housing was made to take a size that was used by Watermota, and could only be obtained from a trade source known to the engineers doing the job.
 
This sounds like the one they fit to smaller beneteaus, no probs wih them and when flooded they are self lubricating.
Stu
 
if you have a pressure fed water supply from your engine that has already been filtered, you should have the better scenario.
In silt and mud, especially if your boat sits in it at low tide, you are going to run the risk of the cutlass bearing getting silted up increasing the risk of wear.
However, if you are always in clear water there should be little problem.
 
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