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Mark Cloutman
Apr 30, 2011 - 7:06PM
Cutlass Bearing
Feverish activity getting Pluto ready for launch mid-May. Ran up engine today in order to bleed injectors following filter changes and got severe vibration from prop. Traced problem to cutlass bearing tube which appears to have slipped c.25mm out of the clamp on the stern tube (which has a split in it) Tube was rubbing against front of prop...
Has anyone out there had this problem?
Is there a drawing in existence that shows arrangement?
Why no nipple on stuffing box?
What do the open tubes on each side of the stern tube do?
Is there supposed to be something (clamp?) between the prop and the cutlass bearing that keeps it in place?
Help!
SeaDog Name (if owner or crew) Pluto (owner)
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John Lansdell
Apr 30, 2011 - 9:36PM
Re: Cutlass Bearing
The cutlass bearing is a metal tube with a "rubber" inner. This unit is slid into a metal socket, bonded into the hull, which at its after end has a split in it, the housing. There should be lugs on each side of the split with a hole in each, allowing a bolt to clamp the bearing into the housing. The material of the bolt should match that of the housing, otherwise there is the possibility of electolytic action between bolt and housing. The bearing normally protrudes a little from the housing, but it could be shortened if necessary. Best thing is to measure the bearing before putting it in the housing. You may have a worn cutless bearing, allowing the shaft to "whip" causing the vibration. If you can move the shaft from side to side, or up and down more than about 1 mm, then it probably needs replacing.
The bearing itself is water lubricated and when the bearing is put in the housing and the holes in the bearing should be aligned with those in the housing to allow water to flow into and through the bearing.
Our stuffing box did not have a grease nipple, but I have put one in. Though it is a pain to do, I would suggest you remove the existing stuffing material and replace it.
SeaDog Name (if owner or crew) Twotails
Graham
Apr 30, 2011 - 10:20PM
Re: Cutlass Bearing
The cutlass bearing on Dougal has been shortened to allow space for an Ambassador rope cutter, and the Darglow feathering prop.
The stuffing box is original and still has no grease nipple or remote greaser. We last re-packed about 8 years ago and we adjust it occasionally (so that it drips one a minute or so. Removal of the old packing can be done use a cheese knife to hook it out (once the forward section is unbolted and slid forwards). Make sure that you re-pack with the same size square section material with plenty of waterproof grease (keenol or similar).
hope this helps
Graham
SeaDog Name (if owner or crew) Dougal
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Eric Richardson
May 2, 2011 - 6:24PM
Re: Cutlass Bearing
Hi Mark
It pays to have about 1/2" of cutlass baring protruding from its housing, this makes it easy to extract when a new one is needed. all you do is grip it with a pair of stilsons and wind it out. As John says it should be retained with a clamp bolt. What John says about drilling is important to get water lubrication to the bearing.
I see no reason to fit a greaser to the stuffing box, we used to have stuffing boxes on centrifugal pumps running at 3000 rpm 24/7/365 with anything up to 1000yds of pressure head, non were grease lubricated, just as Graham said set up to drip occasionaly as a means of keeping cool. On Easy Go the water from the engine cooling water syphon breaker goes into the stern tube just aft of the stuffing. I think thats a good idea as it helps to ensure a water flow through the cutlass bearing and wash out any sand or grit. It also lubricates the bearing when i run the engine with the boat out of the water.
Eric
Eric Richardson
May 3, 2011 - 8:54AM
Re: Cutlass Bearing
Just another thought Mark, once the cutlass Bearing contacts the prop it will prevent water flow passing through the bearing. This will reduce lubrication and the shaft will start to drag on the rubber bearing surface. This will cause vibration as the shaft will bounce around due to trying to stick to the rubber.
Eric
Mark Cloutman
May 5, 2011 - 12:00PM
Re: Cutlass Bearing
Thank you all for your helpful advice.
I have got a plan...
One lug of the clamp has now broken off (John I have e mailed you a photo) so it is now useless.
I am going to wind the cutlass bearing back into place with the lubricating holes aligned (my bearing seems to have a very thin shell but I hope with strap wrench and stilsons I will manage).
I am then going to grind off the clamp lugs and create a wide slot around the whole stern tube in which will sit a new s/s clamp (from automotive world) [I am going to stick the broken piece of stern tube back into place to give even clamping pressure to cutlass bearing]
I will let you know how I get on after this weekend's efforts...
SeaDog Name (if owner or crew) Pluto (owner)
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Mark Cloutman
Jun 10, 2011 - 3:27PM
Re: Cutlass Bearing
Quote: Mark Cloutman
Thank you all for your helpful advice.
I have got a plan...
One lug of the clamp has now broken off (John I have e mailed you a photo) so it is now useless.
I am going to wind the cutlass bearing back into place with the lubricating holes aligned (my bearing seems to have a very thin shell but I hope with strap wrench and stilsons I will manage).
I am then going to grind off the clamp lugs and create a wide slot around the whole stern tube in which will sit a new s/s clamp (from automotive world) [I am going to stick the broken piece of stern tube back into place to give even clamping pressure to cutlass bearing]
I will let you know how I get on after this weekend's efforts...
I completed all of the above with the addition of neoprene isolation between the bronze (?) stern tube and s/s clamp. I then coated all with antifouling making sure that lubrication tubes are clear (and aligned with holes in cutlass bearing). Pluto now back in water and all seems well. As I am on a swinging mooring that dries out, I have been able to check the arrangement and it is looking good.
Thanks again for all helpful advice offered.
SeaDog Name (if owner or crew) Pluto
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