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Old 12-03-2015, 17:34   #1
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Cutlass bearing seizure

Hi Guys...
I have a Roberts25 which was launched around 1984, although I have only owned the boat for about 18mths... I recently had a very expensive repair job undertaken whereby the water lubricated bearing thru which the shaft runs seized up and parted company with the gearbox coupling...ouch, I hear you say... thus tearing the stern gland and allowing way too much water into for the bilges to cope... suffice to say that we were very fortunate that we could get her out and on to the hard very quickly lest we may be diving on her by now...

The underlying reason for this turned out to be what I would call a "serious design flaw"... not something I would have ordinarily attributed to someone with the reputation of Bruce Roberts...
In all boats I have been associated with, this bearing is lubricated via a water feed from the engine intake... in this case, the feed was drawn from two very small flute like intakes either side of the shaft casing where it enters the water...
These flutes, quite predictably, were blocked by growth and hence the bearing ran dry.. I have now had this feed disabled and a new feed from the engine intake engineered so hopefully the problem should not re-occur..

I'm just wondering whether any other boaties, particularly Roberts25 owners, have encountered a similar issue.

Thanks for your time in reading this post

Marc
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Old 13-03-2015, 10:13   #2
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Re: Cutlass bearing seizure

Marc,

If, by "water lubricated bearing" you're referring to a Cutlass Bearing, as far as I know, they're supposed to be fluted, and while I haven't seen much, I've never seen a prop shaft tube being lubricated by water coming from the engine.

Jacques
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Old 13-03-2015, 18:22   #3
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Re: Cutlass bearing seizure

Thanks for your reply Neeltje...

Yes, I was refering to the cutlass bearing...
With respect, Neeltje, my experience is exactly the opposite... I've other boats including a Columbia and there was no fluting... and I can understand why... In tropical waters here in Queensland Australia, the hull growth is so prolific that the flutes would be blocked in next to no time which is exactly what happened... maybe you are from a place where growth is not such a big issue.. don't know
I am NOT a highly experienced marine engineer... just the bloke who has to pay the repair bill and I am not keen to entrust this very expensive bearing to what I would call a design flaw for boats in tropical waters... Bruce Roberts is a very experienced and well regarded boat builder and designer so i don't know why he would have designed the lube system this way for boats in Oz... I have some very long experienced friends who have built and sailed many boats here in Oz, and they share my htoughts on this one...
Thanks for your thoughts on the subject anyway... it is interesting that other boats have this lube method and do not seem to have the same issues... go figure?

Marc
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Old 13-03-2015, 18:44   #4
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Re: Cutlass bearing seizure

Hmm... another ex Qlder cruiser here; had two small boats (30' & 28'); neither had " engine water" injection, both had enclosed cutlass bearing, both had little vents (one with tubes sticking out), neither caused a problem in 10 or so years of Qld cruising. I did keep them clear but it was never a drama to do so. Maybe once or twice a year perhaps or when I was in the water
doing other stuff.

Sorry to hear about your problem though.

FWIW, I never had a problem in the Swan River, Fremantle, Darwin or Indonesia either; all areas of high fouling. Maybe I have been lucky or perhaps you have been unlucky.

Not that it should make a difference, but what sort of system do you have at the other end to keep the water out of the boat - traditional stuffing box, PSS, something else... these also require some water present for cooling!
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Old 13-03-2015, 19:36   #5
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Re: Cutlass bearing seizure

Marc,

From what I've heard, if you already liked the barnacle and vegetal growth you get in OZ, you're just going to LOVE what you get here in Florida!

I have to send a diver down to scrape the prop, rudder and thrusters whenever the boat sits for more than 3 months, just to get it moving properly.

For what it's worth, I had Neeltje's 60-year old bronze cutlass bearing pulled a year ago when I replaced her drive train, and it was the only component they didn't replace.

Jacques
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Old 13-03-2015, 19:43   #6
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Re: Cutlass bearing seizure

ps - My cutlass bearing isn't fluted either. Could that explain things?

Jacques
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Old 13-03-2015, 19:58   #7
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Re: Cutlass bearing seizure

Quote:
Originally Posted by Miss Charlotte View Post
Hi Guys...
I have a Roberts25 which was launched around 1984, although I have only owned the boat for about 18mths... I recently had a very expensive repair job undertaken whereby the water lubricated bearing thru which the shaft runs seized up and parted company with the gearbox coupling...ouch, I hear you say... thus tearing the stern gland and allowing way too much water into for the bilges to cope... suffice to say that we were very fortunate that we could get her out and on to the hard very quickly lest we may be diving on her by now...

The underlying reason for this turned out to be what I would call a "serious design flaw"... not something I would have ordinarily attributed to someone with the reputation of Bruce Roberts...
In all boats I have been associated with, this bearing is lubricated via a water feed from the engine intake... in this case, the feed was drawn from two very small flute like intakes either side of the shaft casing where it enters the water...
These flutes, quite predictably, were blocked by growth and hence the bearing ran dry.. I have now had this feed disabled and a new feed from the engine intake engineered so hopefully the problem should not re-occur..

I'm just wondering whether any other boaties, particularly Roberts25 owners, have encountered a similar issue.

Thanks for your time in reading this post

Marc
Hi my fisher had no water feed to the stern tube when I bought her, and after a while running under engine the prop or shaft would start to vibrate.
The stuffing box had a fitting that had been blocked off, apparently after the original gland material had been replaced with a teflon product (evidently didn't need lubrication) I added a 6mm tube from the heat exchanger to said fitting and all has been good to date.
No more vibration, no excess water past the gland, so I assume that the cutlass bearing was suffering a lubrication or heating problem.
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Old 15-03-2015, 21:51   #8
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Thumbs up Re: Cutlass bearing seizure

Many thanks to all who posted a reply and contributed to natural state of confusion... however, the upside is that I have a better understanding of things and hopefully my cutlass bearing will out live my love affair with Miss Charlotte..

Many thanks again to everyone...

cheers
Marcus
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