Prop Shafts!

[VetChugger]

It appears likely that "Glenmore" will need a new prop shaft. An engineering company has made an attempt to straighten the existing one at no small cost I might add! But, once again, on taking up drive, there is an unholy clattering and vibration from the rear that seems to come from the rear cutlass bearing. Local "sages" are suggesting that the attempted straighten has not worked and the consequent uneven running has worn down these bearings again. Although "Glenmore" has done very limited running since this repair back in July/August 2011, the company that did the work are washing their hands of any responsibility because of the time that has elapsed. Long discussions and concerns fall on very deaf ears!

Anyway, we lifted "Glenmore" yesterday for a look and another engineer suspects either bent or misaligned prop shaft. Both outside cutlass bearings need replacing for sure so the shaft has to be pulled and will be checked for straightness. Some "sages" are suggesting that straightening a bent prop shaft is never 100% successful and that its best to "bite the bullet" or "grasp this very expensive nettle" and go for a new one. Has anyone any opinions on this?

My next question is about a new shaft. It is somewhere in the region of five feet long with a taper at one end at least. The guesstimate of the engineer as to cost of a new one sets ones heart a fluttering seriously! £450!! And that is without any associated labour.

Has anyone any experience of buying a prop shaft? Where from? How much? Who's best to supply?

Any advice at all will be very gratefully received!

Trevor

www.normanboats.co.uk

[MBA Marine]

Go and see Markwell engineering almost opposite Aquafax on Hoveton(Wroxham) ind est.

Also check an double check your alinement.

[diesel falcon]

Sorry but your only option is to replace it , over5 feet it is impossible to straighten to within the original tolerances,you could have it re meltled(sprayed) and re turned but would still be expensive as new, shop around , in this climate you may get a good deal

[Hockham Admiral]

We had exactly this problem several years ago and as has been suggested your only solution is a new one.

However those people managed to suggest to you that the old one could be 100% successfully straightened I have no idea.

Alan Goodchild of Goodchild Marine installed ours.

[Boaters]

We were down at the MTB102 -at Mutford. Today and I remember them saying when we saw them 2 weeks ago that their 15ft shafts were a lot less than that.Try the website for contact details as I do not have them to hand .

[MBA Marine]

Have you looked at the cost of buying a length of A4 S/S bar then taking it to Markwell or Brimblow engineering to machine the taper, thread and key way on it. The price you have just might have a nasty mark up on the material cost.

[diesel falcon]

http://www.metals4u.co.uk/Stainless-Ste ... detail.asp don,t know what size yours is??

[MBA Marine]

http://www.metals4u.co.uk/Stainless-Steel-Round-Bar/40mm-Diameter-303/83/1224/detail.asp don,t know what size yours is??

not 303 or 316 i would only recommend a top grade S/S, but i guess that's not my choice to make, they used mild steel in years passed.

[VetChugger]

Thanks for the suggestions. I'm not looking for a cheap half job, I want a sound and reliable repair. I've seen enough reasoning now to avoid straightening and go for a new shaft. Its just that the prices being quoted are eye watering! But then again, what's new in Norfolk!

Trevor

www.normanboats.co.uk

[diesel falcon]

not 303 or 316 i would only recommend a top grade S/S, but i guess that's not

my choice to make, they used mild steel in years passed.

they do 316 aswell

[quo vadis]

316 is marine grade stainless

[wombat nee blownup]

Perhaps that's how Norwich should line up next Saturday!

[MBA Marine]

316 is marine grade stainless

316 is what most of your rails will be made from, A2 is what most of your bolts that hold them down would be made from and A4 is better for anything under the water.

I was not aware that there was a specific marine grade.

[diesel falcon]

Tought a4 was 316, just another name, if you want higher quality go for a5, but a prop shaft should be ok at a4, a really though stainless is a feric one (f1) but machining it then becomes a problem, these figures relate to the tensile stress/elongation of fasteners , not a property of a prop shaft where the torque value is more relevant,the only reason to make a shaft out of stainless is to stop it rusting,a steel shaft is more than strong enough for the job...but rusts.

Some stainless steel ,is not suitable for salt water use because of it s chemical make up...hence brown staining on cheap rails and screws, 316,a4 is recommended for marine use(salt water aplications)

[mbird]

I must admit I thought A4 and 316 were the same thing. I think the "A" reference is normally applied fixings and 316 (often referred to as Marine Grade) is for stock.

[pks1702]

I had a new prop 'made to measure' and as part of this Clement checked my prop shaft tolerance. I had a full tour of the facility and can't recommend them highly enough.

http://www.clementsmarine.co.uk/propeller-shafts

See the PDF for more info

Whilst 316 series stainless steels are excellent materials for

general use, duplex alloys are now preferred. These alloys

offer much higher strength and are more cost effective than

other high performance stainless steels and more exotic

materials. Consequently, duplex stainless alloy shafts can

safely be designed with substantially reduced diameters

compared to those made of the 316 series, giving the

architect and boat constructor much greater freedom than

previously, and often providing significant weight saving

advantages.

The surprise on the prop was that the 'made to measure' prop cane in less than a Vetus 'off the peg' and the service received stunning.