Stern tube replacement

[Fran]

I have been told we need to replace the 12 pitch stern tube on our 1992 narrowboat as too much water getting in. I understand we will need to replace with a a smaller pitch.

Will the replacement need to be custom made?

Does anyone know somewhere that can do this work in the Napton-on the Hill area?

Or, know someone who can come to a dry dock (in spring 2020) while we are being blacked to do the work?

[David Mack]

What is a "12 pitch stern tube"?

Is your stern tube fitted with a conventional packed gland or one of the greaseless types? If the former then you probably only need to adjust the gland, or perhaps replace the packing. If it is a greasless type you may be able to replace just the seal, or may need the complete gland unit replacing. None of these options would require the whole sterntube to be replaced.

More details of the issue and some photos of your existing sterntube would help to diagnose the particular problem.

[BEngo]

The remarks below apply to a plain bronze stern bearing or a cutless rubber one.  Fancy bearings are different.

 

.Stern tube bearings normally are screwed into a steel ring which is welded into the hull.  The bearing should only need replacing if there is significant wear so that you can feel movement  in the shaft when you push it from side to side and up/down.  You can check this yourself through the weed hatch. If there is no movement you need to look at the stuffing box or greaseless gland, and the bit of the shaft where the gland is, as the shaft may be worn.

 

"12 pitch" may be the pitch of the thread on the bearing, , ( ie 12 threads per inch) where it screws into the hull.  If this is the case you should be able to buy or have made a replacement.  Norris's should be able to help.  Whilton Marina chandlery also had stern bearings on the shelf last time I was in there. No idea of the thread pitch though.

You can check by removing the stuffing box-  grease the bearing really well then undo the fastening bolts and screw it off the bearing.  Do not let the bearing itself turn. Measure the pitch of the thread on the outside of the bearing.  Then refit the stuffing box.  The meaured pitch will be the same at both ends of the bearing.

 

1 in 12 is also the standard imperial propshaft taper for the propeller. Metric onez are 1 in 10 IIRC.  Both are readily available.

N

[ditchcrawler]

A friend of mine had his changed, it was leaking where it screwed into the boss, at Hillmorton, that is not far from you. Failing that I would go to Bottom Lock , Braunston or GUCC also at Bottom Lock

[Tony Brooks]

I am sure Calcutt could do the work but I would want to know far more about why it needs changing. The reason you give seems spurious to me - whatever is causing the leak. Get a second opinion.  When was it last adjusted, when was it last repacked (not greased)?

 

Earlier in the year I ran across a person claiming to be a marine engineer in that area who told me my engine needed attention, as I told him exacty when each of his "cures" had been carried out he came out with a new one. take care it sounds fishy to me.

[BWM]

Our last boat was built in 1992 and also required the stern tube assembly to be replaced. This normally involves the bearing and shaft being renewed, any competent boatyard should be able to arrange this. Not cheap, and i would definitely aim to have it done during the planned dry docking to at least save on the expense of being lifted twice, even if you need to re book somewhere that can carry out the repair. Just repack the stern as needed in the meantime. 

[OldGoat]

Thinks -

If the technician was as dubious as others have suggested - could it be all that is required is to repack the inboard end of the shaft??

 

 

[Slim]

Interestingly I replaced my stern tube, shaft (and other bits) on the slip just north of Cropredy (Richard *****'s) slip in late September. Originally Richard was going to do it for me but in the end I wound up doing it myself. I sourced the parts from Midland Chandlers. Pretty sure the threads on the tube were 14 TPI and that other thread pitch tubes would have been more difficult to source.  If your 12 TPI tube has to be replaced with a 14 TPI one the threaded boss welded into the hull will have to be cut out and replaced.

I replaced the tube and shaft because the stern gland leaked badly. When I pulled the shaft it was really badly worn down from an original 1.5" to 1.2" !! at the packing end. Compared with the new tube the old one was fairly worn, mostly at the inboard end. Heaving on the prop didn't show up any appreciable movement/wear.

As a guide parts cost the following 24" shaft £100, stern tube £68. Had I needed one the stern gland would have been about £170. I think a new boss would have been about £40

I hope the above info will be of help.

 

Frank

[Fran]

Thanks for all your help.

It was Richard just North of Cropredy who told me and showed me that this work needs doing but he really doesn't want to do it himself. The person he recommended (Dale) has gone out of business. Not sure I could or would want to do it myself. And Richard did say I might not be able to use off the shelf parts. So I guess I am looking for someone who has the relevant skills to help and advise and  actually do the work. If I use Richard's slip way I would need someone lined up to do the work in the days available. Or I could use another boat yard to do blacking and investigate my leak and replace stern tube if needed. 

Thanks again

[Neil2]

4 hours ago, Fran said:

Thanks for all your help.

It was Richard just North of Cropredy who told me and showed me that this work needs doing but he really doesn't want to do it himself. The person he recommended (Dale) has gone out of business. Not sure I could or would want to do it myself. And Richard did say I might not be able to use off the shelf parts. So I guess I am looking for someone who has the relevant skills to help and advise and  actually do the work. If I use Richard's slip way I would need someone lined up to do the work in the days available. Or I could use another boat yard to do blacking and investigate my leak and replace stern tube if needed. 

Thanks again

As Tony B says, Calcutt marina are more than capable of doing this and not very far away.  They don't charge the earth for slipping the boat either.  Have a word with Martin in the office there.  

[Boater Sam]

4 minutes ago, Neil2 said:

As Tony B says, Calcutt marina are more than capable of doing this and not very far away.  They don't charge the earth for slipping the boat either.  Have a word with Martin in the office there.  

If you meant Martyn T, he is no longer there, not been for years.  Sadly.

[ditchcrawler]

Or another option is Bottom Lock Braunston who would just pull the back end up the slip on the trolley. I am just wondering if we are talking about the actual stuffing pusher, the type you tighten up with a C spanner.

[Neil2]

Just now, Boater Sam said:

If you meant Martyn T, he is no longer there, not been for years.  Sadly.

No not that one.  There's a "new" Martin, don't know his surname.