Worn prop shaft at Stern gland

[Matata]

The stainless prop shaft we have is worn where the stern gland packing area is. I would guess there was a shoulder about 1/10 mm deep and it is rough and lightly pitted. I haven't put a micrometer on it yet. The shaft diameter is approx 1 1/8". Other than that it is true and in good condition. The affected area could be easily turned on a lathe and tidied up but obviously the lip would be slightly deeper. The strength of the shaft is more than adequate, 20bhp. Another option is to move the sterngland further along the shaft by say 2". We are replacing the sterngland stuffing and the clips anyway and putting on a new hose . Options and opinions would be greatly accepted! Nik

 

[PeterGibbs]

Sounds like you are taking the right course of action - renewing the material bearing on the shaft. But, as you say, it would be better if the worn area is rendered smooth by whatever means - otherwise further damage could arise.

It may not be appropriate, but on my last stern drive boat I had a Volvo seal - the one that is lubricated by sea water - absolutely a major improvement on the old style stuffing and grease seal - ? for you.

PWG

 

[Marsupial]

If you can fit a spacer on the gearbox flange this will mean that the stern gland has new shaft to bear on. Another option is a R&D cushion drive this will also "move the shaft". Obviously you have to make sure the prop has enough room after the "spacers" are fitted.

 

[ianat182]

Suggest that you check the lubrication method on your stern gland and the packing pressure,sounds like one or the other needs clearing/adjusting. Overtightening of the packing may have prevented sufficient lubrication in the packing causing the wear.

ianat182

 

[JohnTH]

It may be possible to "spray" metal on to the worn part of your shaft and then have it turned down to size.

It is possible with ordinary steel but have never had this done with stainless.

73s de
Johnth

 

[pmyatt]

The stainless prop shaft we have is worn where the stern gland packing area is. I would guess there was a shoulder about 1/10 mm deep and it is rough and lightly pitted. I haven't put a micrometer on it yet. The shaft diameter is approx 1 1/8". Other than that it is true and in good condition. The affected area could be easily turned on a lathe and tidied up but obviously the lip would be slightly deeper. The strength of the shaft is more than adequate, 20bhp. Another option is to move the sterngland further along the shaft by say 2". We are replacing the sterngland stuffing and the clips anyway and putting on a new hose . Options and opinions would be greatly accepted! Nik

Have you considered a PSS Shaft Seal?

 

[Matata]

Thanks for the thoughts. i'm happy with the packed stern gland idea and intend to service the present one with new stuffing etc. Then I either have a choice of turning and tidying the present stuffing position and putting the stuffing bock back where it was or make the stuffing box rubber tube say 2" longer and hence moving the stuffing further up the shaft towards the gearbox. I have the length to do this. Which would you do? Ta Nik

 

[Scotty_Tradewind]

Thanks for the thoughts. i'm happy with the packed stern gland idea and intend to service the present one with new stuffing etc. Then I either have a choice of turning and tidying the present stuffing position and putting the stuffing bock back where it was or make the stuffing box rubber tube say 2" longer and hence moving the stuffing further up the shaft towards the gearbox. I have the length to do this. Which would you do? Ta Nik

I have a water fed sterngland by Vetus which I've just fitted instead of a dry seal by vetus.
I now would have preferred a good old greased seal.... at least you know what you'r getting as long as fit and grease are ok.
I'm now fearful that water supply could fail and ruin my new shaft!!

 

[charles_reed]

Cheapest solution would be to leave well alone, replace the seal-packing and cross your fingers that you won't have a leak.

I'd advise against spray-building (which is possible) as the amount put on is probably not deep enough and I've heard complaints from those who've tried, better to have the shaft rebuilt with weld and then re-turned, with a short shaft only slightly cheaper than replacement with a new.

The wear usually is the result of operating in sandy water, I'd suggest checking the cutless bearing area as well, usually not as marked as the gland but equally likely.

 

[doug748]

An extra 2in can't cause a problem? On the other hand the rubber bits are the dodgy things in all stern seals.
If it were me, I would think and worry about this problem and in the end buy a new propshaft. It would probably cost under £60 and as you have to take the thing out anyway..

 

[Spyro]

An extra 2in can't cause a problem? On the other hand the rubber bits are the dodgy things in all stern seals.
If it were me, I would think and worry about this problem and in the end buy a new propshaft. It would probably cost under £60 and as you have to take the thing out anyway..

Very unlikely to get a new shaft for under £60 A blank bar in 316 stainless 1 1/8 inch dia 1m long will cost about that.

I know, I've just bought one.

 

[fishermantwo]

It may be possible to "spray" metal on to the worn part of your shaft and then have it turned down to size.

It is possible with ordinary steel but have never had this done with stainless.

73s de
Johnth

First thing to consider is reversing the shaft. Hopefully you have the same taper both ends, this way you have fresh metal where your stern gland is. SS shafts can be metal sprayed and remachined. My fishing boat shaft has been sleeved with 3 SS sleeves, this is quite easy also.

Check the material type you have for packing, the white stuff is teflon and is fine with SS. The black stuff wears SS shafts, sometimes very rapidly. The last time I had my shaft out I was in Sydney getting new bearings done and the "shop" had several Sydney harbour tug boat shafts in there having metal sprayed on the shafts. They had new packing installed, the black stuff and it wore out the shafts in only a few months.

My shaft had wear but I also went the sleeve method to use more standard size bearings.

 

[Caer Urfa]

Thanks for the thoughts. i'm happy with the packed stern gland idea and intend to service the present one with new stuffing etc. Then I either have a choice of turning and tidying the present stuffing position and putting the stuffing bock back where it was or make the stuffing box rubber tube say 2" longer and hence moving the stuffing further up the shaft towards the gearbox. I have the length to do this. Which would you do? Ta Nik

Did exactly as you suggest, only added another inch to the stern tube rubber length to move the stuffing box position, BUT make sure you fit the correct rubber stern tube! mine has a 3/8" wall from T.Norris, works fine.
http://www.tnorrismarine.co.uk/

Regards
Mike
Archivist for the Colvic Watson Owners Group

 

[cimo]

Thanks for the thoughts. i'm happy with the packed stern gland idea and intend to service the present one with new stuffing etc. Then I either have a choice of turning and tidying the present stuffing position and putting the stuffing bock back where it was or make the stuffing box rubber tube say 2" longer and hence moving the stuffing further up the shaft towards the gearbox. I have the length to do this. Which would you do? Ta Nik

Hello Matata - I would echo fishermantwo's comment. if your installation space allows, consider flipping the prop shaft so you have good shaft surface mating with the stern gland packing. You would need to have the "new" ends modified to suit your prop & gearbox mounting flange though.

I'm thinking about my own engine though, and I would use the oppurtunity to realign the engine while I was on the job.

Alternatively, I have seen grooves welded in, grinded and turned to prefection. A good S.steel welder would be happy to do it for you (make sure he knows its a prop shaft!). This may be the quickest option if you're happy with your current engine alignment.

Can't see any need to extend the flexible part of the stern tube though?

rgds
cimo

 

[Tranona]

Unlikely that end for ending the shaft will work unless it has an identical taper on the half coupling end - most couplings are now clamp fittings rather than tapers. Moving the stuffing box will work. Using a Volvo seal may work depending on where the wear is. A Tides Marine will also probably work, again depending on where the wear is. An R&D coupling (if not already fitted) will move the shaft back 30mm - plenty of room to do this and added advantage is that it will create space for a rope cutter!

All of these solutions are cheaper than a new shaft which will be in the region of £200-250 fully machined.

BTW 1 1/8" is a very unusual size - but it is what it is and may limit your choice of new seals if you want to go that route.

 

[chiefeng]

Nik
A 1 1/8" shaft has plenty of meat on it for the power of the engine and 1/10 mm is bugger all in the big scheme of things. If the seal doesn't leak, then personally I would I would dress the shaft to shamfer(sp?) out any ridge or rough patches then get some nice soft greased packing and re-pack it. With only 0.2mm on the diameter wear you don't even need to use the next size packing. Ask yourself how old is the shaft and how long has it been running in the same location I woud guess around 20 years? You certainly do not need a new shaft.
It certainly won't do any harm to renew the stern tube hose, if it's been there a while make sure you get the correct stuff and don't use exhaust hose! the only thing to be aware of if lengthening it, is the longer it is it becomes more prone to twisting.
Rgds
Bob

 

[Cliveshep]

It's painful on here sometimes - it's like asking for designs for a super race-horse, what you actually get is so many opinions, all different, that you will wind up with a Bactrian camel!

You had the obvious solution from the start, fit a new piece of rubber tube and move it up the shaft an inch or so!

No matter how soft the packing or how much grease or water fed into it, sooner or later the shaft will begin to wear, even as water cut the Grand Canyon or cuts grooves in rocks so soft material will eventually have an effect on hard if it rubs it long enough.

Go change the hose!

 

[doug748]

It's painful on here sometimes - it's like asking for designs for a super race-horse, what you actually get is so many opinions, all different, that you will wind up with a Bactrian camel!

You had the obvious solution from the start, fit a new piece of rubber tube and move it up the shaft an inch or so.

Go change the hose!

Cliveshep makes some good points. I would shy away from some of the more exotic suggestions, which may be fine if you need to save a heavy and expensive shaft but this may not be the case.
Last time I looked at this (same problem as you) I decided on a new shaft (rather shorter, I suspect, and smaller than yours). The cost, machined for prop taper and one end square, was £87.55p (I apologise for the earlier misinformation from memory). It should come in at under £100.