Propshafts needed

[JoeQ]

Both propshafts on my boat are quite badly pitted and either need repaired or replaced.

They're approx 18 feet long by 2.25 inches diameter, tapered at both ends with keyways. There's some photos of the shaft at;

http://www.qitc.net/ketch/Pc090001.jpg
http://www.qitc.net/ketch/Pc090002.jpg
http://www.qitc.net/ketch/Pc090003.jpg
http://www.qitc.net/ketch/Pc090004.jpg

Any comments please on whether repair is OK or if they need to be replaced? Also, depending on which recommendation is made, can you advise on where?

The boat is in Scotland.

Thanks,

Joe

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[charles_reed]

Pretty typical examples of anaerobic corrosion, to which 316 is prone. I've seen shafts far worse than this.

There appears to be little if any wear on tapers or bearing area and in view of the probable cost (£2.5K) of replacement I'd put them back and have another look at them in about 3 years time.

Typical conditions for accelerated corrosion of this kind is an unused boat in a secluded corner of a port where there is little water movement.

You could try having them rebuilt and re-machined - but I suspect the cost of that will be so little different from new shafts that it's probably a waste of time.
One of the leaders in the field are Metallisation Ltd (in the Brierley Hill area).

Why not talk to your freindly local marine engineer - photographs are not the best basis for passing judgement.

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[Johnjo]

Thats a lot of shaft to replace !
Seeing as how they are tapered both ends is it not possible to reverse them around,
so that the good ends sit in the tube.
This is common practice where the shaft is tapered both ends, if that is, the tapers are matching !..


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[JoeQ]

It's not a case of swapping ends, the shaft is pitted along it's entire length so it wouldn't make much difference!

Joe

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[Johnjo]

Sorry did not see that,
All the best with it , mike

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[david_bagshaw]

in the 70s we had bronze shafts machined & remetaled, but the remetaling failed & cracked off!

Just a thought , could you have the shafts machined at the bearing position & undersize bearings made in some manner?



<hr width=100% size=1>David
<A target="_blank" HREF=http://www.euroboating.net>http://www.euroboating.net</A>

 

[oldharry]

Might be worth asking around local engineering machine shops. We we were regularly having to replace shafts on trip boats, as anaerobic corrosion and wear due to shallow water operation would make them unuseable (by commercial standards) in a season or two. A local machine shop made them up for us using the originals as a pattern at less than half the cost of commercially produced ones from stock s/s rod, and at less than half the cost of the local marine engineering stockist 'off the shelf' ones.

All that is needed is to find a supplier of rods of suitable material and diameter, and a friendly machine shop with suitable lathe and keyway cutter.




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[JSB]

Hi Joe

I have a prop shaft which did snap, I have a photo showing the local pitting and the break, yours seem in good condition in comparrison, if you want a copy send me your email address mine is johnben@ntlworld.com.

John

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[JSB]

Hi Joe

I have a prop shaft which did snap, I have a photo showing the local pitting and the break, yours seem in good condition in comparrison, if you want a copy send me your email address mine is johnben@ntlworld.com.

John

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[Gordonmc]

Joe,

Youre user profile doesn't give anything away about your location in Scotland, but this might help if you are in the Clyde area...

My shaft suffered crevice corrosion at the prop. end which ate away a hole in the threaded end. I had a replacement made up by Smillie and Cuthbertson in Kilmarnock by taking the old one in, plus the prop. to make sure of the taper. They had the new one made up in under a week.
They even managed to source imperial sized 316 stainless steel bar.
I have no association with the company but have used them satisfactorily for other fabrication and welding up a mast.
Try them on 01563 521819.


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