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Is it possible to have scale/calcification build up on the prop shaft inside the cutless bearing that causes a vibrating/chattering noise from that area in forward and reverse that goes away with use?

 

Ok at low revs worse at moderate to high revs. Prolonged low speed use makes the noise go away.

 

Boat = 36’ timber yacht, 5 yr old / 150 running hour rubber bushed kind of cutless bearing with normal play and  2205 s/s shaft also 5 yr old, bronze prop, no anode, run in fwd and rev gear 2 x month minimum for 30 minutes

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Thanks for input..Checked alignment, deadwood cutless bearing= bronze tube with rubber bush.

The noise goes away with motoring use....

 

Is hard growth on the shaft possible?

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There is a number of different things that can cause this. You didn't say of the prop was fixed or folding. The props that have blades that are independent of one another can open slightly differently if a shell or weed is stuck somewhere. Growth on the prop or shaft as Steve has said. It's one of those things where you need to haul the boat and check everything over. Simply because there are so many different possible answers.

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Prop is fixed 3 blade. Prop speed in good condition. Recent water blast. As the noise goes away with use there is a variable. The only one I can think of is hard growth on the shaft bearing surface.

 

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I doubt any growth in the bearing causing such an issue. It would tear the bearing surface apart.
It's the fact that the noise goes away that is throwing out of my mind many possibles, including several posted above.
The only other thing is that you are getting growth on the prop speed and then running the engine is throwing the critters off the Shaft/Prop, which is how propspeed works. It doesn't stop growth at all. It just means they can not get a hold and are thrown off.

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The only other thing is that researching this I realised the cutless bearing has a brass shell part number which will be in contact with the copper stern tube and if it really is brass it will be breaking down. (5 yrs old) No anode fitted anywhere.

So will replace with a phenolic one and have a good look at everything at that time (now soon)

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Over anoding a wooden vessel can cause the wood itself to deteriorate. Proper levels, no issue that I know of... The issue of no anodes is not "just a prop" but every immersed piece of metal.  Every owner must make an assessment of whats best for them.

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No anode,ever had one?? easy to fit,lots of wooden vessels have it attached to keel,how much room betweem prop and hull??can get collar type andoes,h28s are a good example of fitted collars.

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Getting bit off topic here because what I would like to know is and my original question is .....has anyone seen scale/calcification build up on the prop shaft inside the cutless bearing?

But re the anodes rule - number one is don't mix metals under water - lots of info at Waitemata Woodys

https://waitematawoodys.com/2015/05/15/electrochemical-damage-to-wood-the-marine-version-of-leaky-homes/

 

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15 minutes ago, ricka said:

Getting bit off topic here because what I would like to know is and my original question is .....has anyone seen scale/calcification build up on the prop shaft inside the cutless bearing?

But re the anodes rule - number one is don't mix metals under water - lots of info at Waitemata Woodys

https://waitematawoodys.com/2015/05/15/electrochemical-damage-to-wood-the-marine-version-of-leaky-homes/

 

But you have. Fasteners, through hulls, shaft, rudder and shaft, prop, cutlass bearing maybe, rudder bearings maybe, all very unlikely to be the same.

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Fairly sure we have had scale on the shaft under the cutless bearing. We put in a new shaft when we did the engine. We had scale on the taper, cause that wasn't mated properly when we changed a prop. I doubt scale would cause what you describe, but it could be a symptom. Scale under the cutless bearing is likely to accelerate wear of the bearing, once it gets sloppy you get all sorts of random noise. Generally just lots of noise and vibration. But you can get structure born vibration that makes very odd noise in other nearby parts of the boat. Before we last changed out cutless bearing, I was regularly looking in the lazarette locker for something that had come loose.... there was an odd rattle.

The other thing it could be is prop cavitation. Its unlikely, unless you've changed your prop, or have somehow changed or damaged the very tip of a blade. Cavitation is when the prop tip is too close to the hull, sounds like a high pitched 'pinging'. As revs increase you can't hear it, the frequency increases until its just more white noise... Can normally only hear it on clam still days at low to medium revs, i.e. its very hard to hear over the environment. If you are familiar with large pumps (water or wastewater) it is the same noise / phenomina as when a pump impellor is worn, or the pump is dead-heading (stalled but still spinning around).

I would change your cutless bearing first. A warn bearing causes all sorts of noise and vibration in the drive train. The brass ones are fine, the phenolics are cheaper but don't last nearly as long. We have a pulling tool if you want, and it fits your boat. We do ours between tides on piles. Takes two of us less than 10 mins from start to finish, and no need to drop the rudder, haul out and all that bullshit. The tool fits 1 1/4 inch shaft, 1 3/4 bearing. Pick up Whangaparaoa.

On the anode question,  I understand why you want to avoid risk of over zinc-ing, we have had soft wood cut out cause of over zincing, (DD kauri with glass skin), but we now only have a zinc on the prop shaft. I know the classics banned anodes, complained a kiwiprop failed after 3 years, but no anode...

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15 hours ago, Island Time said:

But you have. Fasteners, through hulls, shaft, rudder and shaft, prop, cutlass bearing maybe, rudder bearings maybe, all very unlikely to be the same.

Yes but all those are isolated eg there are no mixed metals in contact with each other under the water.

Fastners are isolated, bronze though hulls are isolated, s/s rudder shaft is isolated from bronze bearing at the lower end.

There is an electrical path with resistance from the prop shaft to the stuffing box and cutless bearing - not sure why except perhaps because they are close to each other and the salt water is conducting.

The only thing that isn't isolated is the prop and shaft which are dissimilar metals and the prop degrades over time but will last for 10 years or more and that works out at $120 per year minus the cost the cost of replacing anodes.

The boat was built 50 years ago with no anode allowed for

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15 hours ago, Fish said:

Fairly sure we have had scale on the shaft under the cutless bearing. We put in a new shaft when we did the engine. We had scale on the taper, cause that wasn't mated properly when we changed a prop. I doubt scale would cause what you describe, but it could be a symptom. Scale under the cutless bearing is likely to accelerate wear of the bearing, once it gets sloppy you get all sorts of random noise. Generally just lots of noise and vibration. But you can get structure born vibration that makes very odd noise in other nearby parts of the boat. Before we last changed out cutless bearing, I was regularly looking in the lazarette locker for something that had come loose.... there was an odd rattle.

The other thing it could be is prop cavitation. Its unlikely, unless you've changed your prop, or have somehow changed or damaged the very tip of a blade. Cavitation is when the prop tip is too close to the hull, sounds like a high pitched 'pinging'. As revs increase you can't hear it, the frequency increases until its just more white noise... Can normally only hear it on clam still days at low to medium revs, i.e. its very hard to hear over the environment. If you are familiar with large pumps (water or wastewater) it is the same noise / phenomina as when a pump impellor is worn, or the pump is dead-heading (stalled but still spinning around).

I would change your cutless bearing first. A warn bearing causes all sorts of noise and vibration in the drive train. The brass ones are fine, the phenolics are cheaper but don't last nearly as long. We have a pulling tool if you want, and it fits your boat. We do ours between tides on piles. Takes two of us less than 10 mins from start to finish, and no need to drop the rudder, haul out and all that bullshit. The tool fits 1 1/4 inch shaft, 1 3/4 bearing. Pick up Whangaparaoa.

On the anode question,  I understand why you want to avoid risk of over zinc-ing, we have had soft wood cut out cause of over zincing, (DD kauri with glass skin), but we now only have a zinc on the prop shaft. I know the classics banned anodes, complained a kiwiprop failed after 3 years, but no anode...

Ah huh - brilliant then that's the problem! and I will replace the cutless bearing. Last time I removed it with a slide hammer cutting a slot in it first with hand held hacksaw blade. The boat has the prop in an aperture which is a bit of a bugger cos to get the shaft forward enough to remove the bearing the engine has to be lifted and moved forward or possibly get away with removing the gearbox (uncharted territory).

Thanks for the offer of the puller might take up you up on that - the size is right. Would you be able to send a pic and I can quickly see if it will be of use due to the small prop aperture size.

The tip clearance etc is correct enough according to the prop guys.

 

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Old bearing coming out.

The parts for this cost less than a travel lift, lift and hold... for any lurkers out there wanting to make their own. This one is 1 1/4 inch by 1 3/4. We have loads of space between the strut and hull, so haven't trimmed down the threaded rod, but it only needs to be twice as long as the bearing, plus plate thickness's, washers and nuts.

Scaffold tube cut in half, held together with cable ties to get started, pushes the bearing out of the strut.

Threaded rod from Bunnings (or any more reputable hardware store).

The key part is the plates. We got these made at a local engineering fabricator. Painted them ourselves with a can of something in the shed that protects from corrosion.

Then all you need is 2 spanners. If there is two of you working on it, take 4 spanners... takes maybe 10 minutes to change a bearing from go to wow, including taking photos. If you get a brass bearing, freeze it, keep it on ice in a chilly bin, and it will slide in 3/4's without evening having to push it. Once it warms up it sticks in nice.

20191028_132815.jpg

20191028_132821.jpg

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