Stern gear tube

[John Lewis]

Hello all, thought maybe I'd ask on here if anyone may know a bit about stern tubes, bearings etc.

 

Pics below will show I have had to remove my prop shaft as it was stuck in situ, and not rotating.

 

Some locals told me the boat sat idle for years, never running, and when brought out on land may have run.

 

This bronze bearing seems to be a sleave type I believe, which I think would spin with the prop shaft, inside a brass/bronze outer bearing.

 

There was very little grease inside the tube when I knocked it out, so clearly wasn't getting lubrication down.

 

Its not a water cooled cutless bearing, but having spoken to Exalto bearings in Derby, they suggested converting over to a water lubricated gutless bearing,

 

at a price of about £259.

 

But Im tempted now to perhaps keep what I have, maybe skim it down if I can find an engineer?

 

What do you think?

 

Thanks, 

[Tracy D'arth]

Its an unusual bearing set up, not seen one quite like this before.

The steel shaft should be free to rotate inside the bronze bearing that at present seems to be seized onto the shaft. It needs to be removed and cleaned up.

The bronze bearing should be locked tight in the tube in the stern post.

The clamp that holds it is outside, my experience is with the bearing being held by a screwed clamp sleeve inside the hull, but the principle is the same.

[BEngo]

You do not want a cutless bearing.  The sand, mud and grit inherent in canal boating do not often get on long with a water lubricated rubber bearing.

It looks to me as though an original white metal lined stern bearing has failed and a smaller shaft and bearing have been fitted inside.

The two hole flange with gits seal has a screw thread inside.   Does this screw onto the bit of fixed bearing that sticks out of the stern post?  Otherwise what makes the shaft concentric with the seal?

 

Looks to be an old boat with a forged stern post.  Who built it?  Someone on here will probaby know the original set up.

 

I think the answer has to involve separating the tail shaft and the bearing currently siezed to it.  You can then judge the state of the shaft  and that bearing before deciding on the way ahead.

 

The Roller of a solution is a new stern bearing, tailshaft and stuffing box, all fitted into a threaded ring welded onto the existing  stern post flange with two holes.

 

If the shaft and bearing are good enough to clean up, there is likely then  to be too big a gap between the shaft and the bearing once they have been cleaned up.  Shaft sleeves are available, or  ir should be possible to get the bearing re metalled to match the cleaned up shaft.  The cost is likely to be as much as a new shaft, bearing etc.

 

Don't buy a Vetus replacement!  Decent kit, but well over priced.   Talk to T Norris Marine of Isleworth.  They are on the web. Usual disclaimer.

N

[Tony Brooks]

I am with BEngo re the Cutless bearing for canal use. I suspect that you once had  a grease cap on the gland rather than a remote greaser because the Git/lip seal could easily get pushed out by the grease.

 

I suspect that rather than trying to make what you have serviceable it might be easier to fit a completely new stern gear - I agree Norris

 

Photo of the inside of the boat?

 

 

[John Lewis]

1 hour ago, Tracy D'arth said:

Its an unusual bearing set up, not seen one quite like this before.

The steel shaft should be free to rotate inside the bronze bearing that at present seems to be seized onto the shaft. It needs to be removed and cleaned up.

The bronze bearing should be locked tight in the tube in the stern post.

The clamp that holds it is outside, my experience is with the bearing being held by a screwed clamp sleeve inside the hull, but the principle is the same.

Ah right, I wasn't sure which parts moved. 

But the inner brass part or bronze not sure, has no corresponding slot to line up with outer brass/bronze bearing.

Looking at it there are two grooves cut on the outer, but nothing inside.

If I could remove it off the shaft perhaps I could get them cleaned up and just locktite them together?

 

It was built in some school in Nottingham in 70s, don't know much more than that.

 

Apologies,

 

The shaft is 1 3/4" and steps down to a 1 1/2" , to Lister SR3. All seems fine engine side.

 

thanks.

[Tony Brooks]

Thanks for the photo. It does not seem there is any form of greaser so how that lasted with plain metal bearings I have no idea.

 

I think this might be a bitza because I can't see the male thread than ,ates with the thread in the external housing. It may be in the end of the brass stern tube.

 

I would expect the brass stern tube to unscrew from the housing on the stern post once you free the stern gland. If it does you may well be abale to screw a modern assembly into it with the bearing installed in the usual way.

Edited May 27, 2020 by Tony Brooks

[John Lewis]

There is a greaser, just not in photo Tony.

 

Yes the photo at top should show there is a third part, a brass cap which threads on keeping the bearing in place,

Then the prop goes on. There was a rubber inside this Believe.

 

What is a modern stern gear?

Could you share a link...

[Mike Adams]

This looks like a typical stern tube as fitted in a wooden boat. Each end of the brass  tube should be threaded with the outboard bearing collar being held in by the threaded part also containg some packing. The whole of the tube would be full of grease and it looks that maybe the whiteish nylon tube going into the brass sterntube partway along would have supplied the grease. On a wooden boat the end cap would have been screwed up tight and then held in place by a couple of coach bolts. It is not clear from the picture if the outboard threaded part remains in place - maybe not so the end cap is just held on by the two bolts in the hull. I think it may clean up and be useable.

[John Lewis]

18 minutes ago, Mike Adams said:

This looks like a typical stern tube as fitted in a wooden boat. Each end of the brass  tube should be threaded with the outboard bearing collar being held in by the threaded part also containg some packing. The whole of the tube would be full of grease and it looks that maybe the whiteish nylon tube going into the brass sterntube partway along would have supplied the grease. On a wooden boat the end cap would have been screwed up tight and then held in place by a couple of coach bolts. It is not clear from the picture if the outboard threaded part remains in place - maybe not so the end cap is just held on by the two bolts in the hull. I think it may clean up and be useable.

Yes Mike, you could be right.

 

Perhaps the whole thing is salvage able? I dunno,

I tried removing the bearing from shaft with a pullers ,but would come. 

 

 

[Tracy D'arth]

The more I look the more I think its a botch up.

I think that the outer screwed part of the bearing is missing. That there is no greaser would suggest that it would not work long. The bearing seized on the shaft is a standard bearing sleeve off a conventional stern assembly that fits from the inside into a welded in boss outside on the stem post.

 

I would suggest staying with a stuffing box on a  canal  rather than a flexible water fed seal, there is too much grit in the water.

[Mike Adams]

I am sure you can get the two parts apart. Some penetrating oil ,leave for while, heat up the bearing sleeve with a blowlamp and use a piece of hardwood and a hammer alternately on each end of the sleeve until it moves and a bit more oil and I am sure it will shift. You may find the shaft will clean up  just  up with say a paint cleaning/prep wheel on a drill/grinter will give you a reasonable finish on the shaft, some gland packing in the end and it will go on for years.

[John Lewis]

33 minutes ago, Mike Adams said:

I am sure you can get the two parts apart. Some penetrating oil ,leave for while, heat up the bearing sleeve with a blowlamp and use a piece of hardwood and a hammer alternately on each end of the sleeve until it moves and a bit more oil and I am sure it will shift. You may find the shaft will clean up  just  up with say a paint cleaning/prep wheel on a drill/grinter will give you a reasonable finish on the shaft, some gland packing in the end and it will go on for years.

Yes, it did budge a mm or 2 athirst Mike.

I may get someone with a blowtorch to help, 

 

Tracy, there is a grease nipple on the inside of stuffing box, and a greaser.

 

So do I go ahead and remove and clean up?

 

Also why would it be stuck in the first place?

 

cheers

Edited May 27, 2020 by John Lewis

[bizzard]

I f heating is needed to remove that sleave, you need to do it fast to prevent the shaft getting as hot. Run the blowlamp flame back and forth along one side of it only for quick expansion which will leave the shaft relatively cooler.

[BEngo]

4 minutes ago, John Lewis said:

, 

 

So do I go ahead and remove and clean up?

Remove it, and lets see what we see then.  The state of the shaft and the bearing are otherwise not known, but the latest picture of the screwed projection on the outer tube, which fits the (unnecessary ) outer seal, and the great length of the stern tube compared with the bearing length convinces me that someone has sleeved a larger stern tube.

I remain to be convinced that clean up and refit will either last long, or be cheaper than a renewal, unless you can do a lot of the work yourself.

 

 

Something has also  caused it to seize,  and even sitting around for years should not do that, so that must also be cured, or it may do it again....

 

N

  

 

 

 

[Mike Adams]

12 minutes ago, John Lewis said:

Also why would it be stuck in the first place?

Even if the shaft is stainless if there is water and a lack of oxygen it will corrode. It may be good sign if it is stuck for if it was very worn it probably would not have siezed. It may be mid steel so again it will corrode in the air with no grease on it. Once these things move a bit a bit of patience and care will free it up.

[John Lewis]

20 minutes ago, BEngo said:

Remove it, and lets see what we see then.  The state of the shaft and the bearing are otherwise not known, but the latest picture of the screwed projection on the outer tube, which fits the (unnecessary ) outer seal, and the great length of the stern tube compared with the bearing length convinces me that someone has sleeved a larger stern tube.

I remain to be convinced that clean up and refit will either last long, or be cheaper than a renewal, unless you can do a lot of the work yourself.

 

 

Something has also  caused it to seize,  and even sitting around for years should not do that, so that must also be cured, or it may do it again....

 

N

  

 

 

 

I'll try and get help removing it here, and post back. thanks.

 

I reckon, lack of use, and maintenance, left the tube with no grease down there,

Perhaps out of water, and its a carbon steel shaft theres been a bit of expansion from rust?

I dunno,

 

I did feel like it was catching near the bearing, and there was about an inch of play originally.

 

 

Thanks all.

[Tony Brooks]

9 hours ago, John Lewis said:

I'll try and get help removing it here, and post back. thanks.

 

I reckon, lack of use, and maintenance, left the tube with no grease down there,

Perhaps out of water, and its a carbon steel shaft theres been a bit of expansion from rust?

I dunno,

 

I did feel like it was catching near the bearing, and there was about an inch of play originally.

 

 

I can't see any evidence of a carbon shaft seal and I can see evidence of the adjusting studs for a stuffing box.

 

I have been thinking about this overnight and agree its very similar to the stern gear we ha don the wooden hire boats (Thames). The major difference is the hire cruisers used Cutless outboard shaft bearings and their housing (the equivalent of the bit you unscrewed from the back) was much longer than yours plus it had two small water scoops at the front end to allow water lubrication in and a couple of grub screws in the side to secure the bearing.

 

I note the bearing seems to have a land around the outboard end. Is this clamped against the end of the threaded tube by the housing you have taken off?  If so then that will locate the bearing at the back of the tube but totally prevent the bearing turning. Is the bearing long  enough to allow a bolt of some sort to be put through the tube inside the boat to fit into the cut outs at the end of the bearing? If so great care will be needed to ensure it fits deep in the cut out yet is clear of the shaft yet is water tight.

[Alan de Enfield]

51 minutes ago, Tony Brooks said:

he major difference is the hire cruisers used Cutless outboard shaft bearings and their housing (the equivalent of the bit you unscrewed from the back) was much longer than yours plus it had two small water scoops at the front end to allow water lubrication in and a couple of grub screws in the side to secure the bearing.

Like this ?

 

 

 

[Tony Brooks]

6 minutes ago, Alan de Enfield said:

Like this ?

Exactly like that.

[Alan de Enfield]

2 minutes ago, Tony Brooks said:

Exactly like that.

They are on my cruiser, but I don't think I've ever seen anything like them employed on a NB

[Tony Brooks]

9 minutes ago, Alan de Enfield said:

They are on my cruiser, but I don't think I've ever seen anything like them employed on a NB

Which is what I would expect unless such a boat was built for large river use only where the mud and grit stays a long way below the prop for most of the time. However I am sure there must be some around, especially as it seems a supplier (who should know his stuff) recommended a Cutless bearing, but how that was to be lubricated I have no idea.

[John Lewis]

Well it tapped off, still was tight fit.

Maybe clean it up, Welder here suggested we get a local to skim the shaft slightly?

 

 

 

[Tony Brooks]

5 minutes ago, John Lewis said:

Well it tapped off, still was tight fit.

Maybe clean it up, Welder here suggested we get a local to skim the shaft slightly?

 

If you do that you may need a new bearing machining up. If I could not get the shaft in a lathe I would spend an hour or two with various grades of emery cloth to get all that block off and the see how the bearing spins on the shaft.

[bizzard]

3 minutes ago, John Lewis said:

Well it tapped off, still was tight fit.

Maybe clean it up, Welder here suggested we get a local to skim the shaft slightly?

 

 

 

Probably no need to have it skimmed. Just a sheet of very fine emery ot production paper to clean it up, encircling it and grasp it by hand, twisting back and forth all around like  a motorbike hand throttle twist grip.

[BEngo]

Skimming it will take too much off, unless you have it ground.  Use  Emery tape.  25  mm wide, various grades, comes in rolls.  Start with 120  grit to get the oxidation off, then work through the grades to about 320 or 400.

Wrap one  turn, no more  and just draw it to and fro and slowly move along the shaft.    Only the bearing area needs doing.  You want fine  scratches round the shaft  not along it.  MSC Industrial Supply do a good selection of emery rolls on line next day.

 

Check the size of the shiny portion, inboard end.  That is where the packing in the stuffing box runs. It should not be more than about 20 thou smaller than the shaft.

 

What is the inside of the bearing like?

N

Edited May 28, 2020 by BEngo