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Old 04-06-2014, 01:20   #1
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Calcification on shaft

We have a catamaran with 1 1/8 inch - 1mtr shafts. Dripless seals. Cutless bearings at end of shafts with water being pumped through for lubrication. Shaft Anodes are about 6ml back from the cutless bearings, then prop.
Our problem is - we have calcium/mineral buildup occurring on the shaft in the water cooling channels of the cutless bearing on one shaft only. We have to drop the shaft back and scrape the build up off. The water quality is the main perpetrator. Have done it 4 times in last year. Presently in Kuah Langkawi. Can't understand why one shaft but not the other.
Anyone experience this before?

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Old 04-06-2014, 03:26   #2
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Re: Calcification on shaft

Freshwater discharge on the other shaft?

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Old 04-06-2014, 03:42   #3
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Re: Calcification on shaft

that is a mystery,differant s/s material in shafts!
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Old 04-06-2014, 07:11   #4
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Re: Calcification on shaft

Do you have a drive-saver on one coupling, or any other difference between the two that would cause one shaft to be more electrically isolated than the other?

I am thinking about the possibility that your calcified shaft is over-protected by the zinc.

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Old 04-06-2014, 07:41   #5
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Re: Calcification on shaft

What is the source of the cooling water for each shaft?

And are both systems plumbed the same.

If there is a temperature difference between the two, or if one shaft runs hotter then the other.
If you have a laser heat gun check the system while it's running.
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Old 04-06-2014, 09:15   #6
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Re: Calcification on shaft

Thankyou everyone for your replies.
There is nothing different that we know of between the two shafts and their mountings. The cutless bearing is salt water cooled.
The only way there could be stray current is through the water intake. The Shaft is completely separate to the engine. We have a rubber flexicoupling between shaft and gearbox.

Hi Mark

We have the recommended annodes. The boat was in the water 4 years before this first occurred. First time in Cairns and it siezed the shaft in the cutless bearing because of the ridges of build up.

We will try taking the annode off the shaft and see what happens. We have also considered turning off the water intake incase there is some kind of electrical think going on.



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Old 04-06-2014, 09:43   #7
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Re: Calcification on shaft

How can it build up if you run the shaft? Maybe you should run it a bit every couple of days...?
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Old 04-06-2014, 22:58   #8
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Re: Calcification on shaft

Yes that is the 1st mate's thinking as well and we did not get it happening when we went through Indonesia. However Indo's water was a lot cleaner and did not have limestone sediment. First mate thinks running it once a day may solve the problem. I ran it regularly about every 4 days in Ao Chalong and it built up over about 6 weeks. Ao Chalong is noted for polluted water. We sat for three months in Johor Bahru another very oland.ran the prop about once a week and it didn't happen.

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Old 05-06-2014, 00:40   #9
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Re: Calcification on shaft

Crusty shaft. Not a good look. Have you tried polishing it?

Sorry, couldn't help myself.

Enjoy Langkawi, lovely spot
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Old 05-06-2014, 09:00   #10
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Re: Calcification on shaft

Thanks for the tip!

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Old 13-06-2014, 01:26   #11
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Re: Calcification on shaft

I used to have a 316SS shaft electrically insulated from the engine through a flexible coupling and it built up calcium as you describe.

One day I threw away the flex coupling that was just helping with shaft vibration, made a new shaft out of 2205 stainless that is now electrically connected to the rest of the engine and... I haven't seen calcium deposits since. Go figure!

It is quite common, the answer is rotating the shaft periodically, even by hand, to scrape the deposits gently before they get too thick and too hard.

There have been many cutless bearings destroyed on boats that had been sitting around. I really like turning the shaft by hand to feel what is going on if the engine hasn't run for a while, it is a lot easier than replacing the cutless bearing. Once you start chewing into it, deposits form all around the shaft instead of in the grooves only and that is usually the end of it.
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