Noisy Cutlass Bearing

[RJD]

Hi, any comments on what sounds like a noisy cutlass bearing would be appreciated.
I have installed a new shaft, cutlass bearing and reduced to a 2 bladed prop on my Westerly Konsort. Engine alignment is correct but there is a noise emitted by the cutlass bearing in the 'P' bracket which was not present last year. A rope cutter is present which was fitted to last years set up.
The noise was very noticeable after the boat had been left on it's swinging mooring for a two week period.
Do shafts and bearings need running in?
Thanks in anticipation. TonyP

 

[JOHNBOY]

Do your best to discribe the noise.
My boat rumbles like a train and so far .........we'r not shure what it is.

 

[RJD]

A low frequency rumble/grumble....almost as if a handful of gravel had been added to assist with lubrication! Fairly uniform across entire rev band but perhaps less noticeable at 1850 rpm (engine)
Tks, Tony

 

[mtb]

Sounds as though it could be some thing to do withy either the rope cutter or prop .
cutlass bearings are made to suit the shaft size and as long as they are in water thus lubricated it should be end of .

But after two weeks on swinging mooring !! was it only after this and not before .
Is the prop to big and not enough clearance between the hull .
Has the rope cutter or cutlass bearing moved mmmmmm this could be possible .
Get it out for a look .
Mick

http://homepage.ntlworld.com/boats
I want a big steel ex trawler / tug v / cheap or swap for tug

 

[pandroid]

Are you sure its the bearing? If you have changed prop size perhaps it could be cavitation. Some props make more noise than others. Is performance the same?

 

[Sinbad1]

Sounds strange this one. If it cavitation you would expect this noise to increase with the revs as cavitation is caused by pressure differential between front and back of blade. Did you put lots of grease on the shaft where it lies in the cutless bearing. If not I would suspect that you have a couple of molluscs which have taken up residence in new bearing. This is not uncommon when boat has been left with shaft unturned for a period and when you start the prop/shaft turning they fragment and get imbedded in the cutless rubber and you could get a gravelly sound. (Also will ruin both bearing and shaft-just to cheer you up)

Suggest you tie rope to prop and remove it. Then run engine/shaft and you will know if its the new prop shape/location. Work from here.

Also possible that prop is sitting further outboard than old prop and you may have a little bit of 'whipping' on the shaft. First try taking the prop off.

 

[david_bagshaw]

Low rumble & vibration sounds to be from the reduction in number of blades, & a harmonic with the engine cylinders / gearbox.

we lost a low speed rumble on changing from 3 to 4 blades with 6 cyl engines, so the reverse might be your case.

Cutlass bearings usually dont need running in and when miss aligned sometimes give a whine, particularly on longer shaft setups.

goodluck

David
www.euroboating.net

 

[JOHNBOY]

RJD
Hi..... We are in the same club.... I've also changed my prop for this season sounds like the type of noise.... My thought is cavitation ?
My engineer (pro) is comming out to listen this weekend. I will let u know his opinion.
Keep in touch. JOHNBOY

 

[RJD]

Thanks to all for your replies....the weekend ahead has been planned. I just have to decide whether to grovel in the mud at low water or pay the price of a lift!!
The molusc theory seems quite likely to be correct but all other possibilities remain open.. thanks to all for replying
Tony P

 

[jfkal]

Could be barnacles growing in the grooves. Mine also rumbles for a while if left alone for a week or two and then fades after a few revs in gear. Growth on the propeller has a similar effect however does not fade, except after major scrubbing (.

 

[RJD]

Having dried out over the weekend (boat that is!) on a suitable sandy bit.., I found that the shaft had been attacked by a large number of small barnacles. Some of which had blocked 3 of the water ways thru the cutlass bearing. A cycle spoke with a flat filed down one side was inserted down the waterways followed by a squirt of PTFE lubricant. I cleaned the shaft and re-antifouled it. On getting underway, all was well...groaning and graunching no longer present.
Thanks very much to all who replied, comments were much appreciated.
Good sailing..
TonyP