Advice on replacing C28 shaft log

[lockie]

I had a nasty surprise today as I was going about replacing the stern tube hose and fitting new gland packing: the shaft log tube was badly dezincified where it projected into the boat, and part of it fell apart. I managed to get the old hose back on and clamped to the remaining sound first centimetre or so where it emerged from the glass. That stopped any leaks, but it's far from robust and not up to any significant forces, so I will have to replace the tube.

Has anyone here done this, or had it done? I've looked at a few Youtubes and it doesn't look too difficult to just glass in a new tube. My problem is how do I align the new tube with the shaft?

Any help would be appreciated. 

Cheers, Graeme

[Mando C29]

G'Day Graeme,

I went down this track on Mando which I assume would be the same or a least very similar to a C28!

On Mando, there was a copper sleeve (tube) that had been glued/fiberglassed into the hull. This, of course, housed the cutless bearing for the drive shaft. In my case it had been badly eaten out through corrosion/electrolysis??

I was able to draw out that tube ( difficult) and insert a new copper tube of the correct diameter. I believe copper tubing is all imperial measurements so the imperial to metric change-over shouldn't be a issue. (I could be wrong on this!)

Once I had installed the tube (in my case I Stikaflexed in it) and installed a new cutless bearing, I then went down the track of aligning the drive shaft to the tube. If the motor has been running with negligible vibration then you may not need to do anything at all!

I am assuming you have the original set-up (that I had) of a truck radiator hose clamping on the fibreglass "nose" at the stern end and the other end of the hose containing the packing gland and clamping nut.

The clamping of the hose to the fibreglass is (in my opinion) a real weakness as you are trying to clamp a round tube onto a tapered moulding! The best you can do here is push it on a far as you can then put 2 hose clamps around it!

If the drive shaft coupling needs aligning to the motor coupling this is how I went about it. (hope I'm not boring you to death!!)

The problem/challenge is that the drive shaft (in the radiator hose configuration) has no fixed position. This is because you have a flexible rubber bearing at one end (cutless) and a radiator rubber hose at the other end ie the shaft can move around quite a bit. What I did (and it's all feel) was to move the shaft up then down, then side to side and try and determine the most central position. I then (not easy) braced the shaft in that position with timber packers so that were it sat was as close to central as I could get it. (This is NOT a 5 minute job)

I then went through the process of aligning the motor coupling to the shaft coupling so that there was no more than

4 thousand of an inch (0.1mm) difference all around.

The end result was that I could run my motor to 3300rpm with very little vibration.

This work is definitely a 2 man/woman job for 2 reasons: 1. To pass the tools whilst you are screwed up in the back of the boat and 2: To constantly tell you that the pain won't last forever and it will be worth it in the end!

Hope all this helps and good luck,

Cheers,

Maurice. 

[Maeling]

Thanks Maurice, as usual you have it pretty-well covered.  Just remember you (as in others)  have the diesel jumping around on flexible mountings and self aligning the shaft as it spins.  It is a job where you just have to accept the best possible  result.

Regards

Geoff Raebel  aka scoutair

[Graeme Lock]

Hi Maurice;

Love to hear how you got the tube out. That might make it a lot less scary.

Cheers, Graeme

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[Mando C29]

Graeme,

I assume the boat is out of the water. Can you send me a photo of both the inside and the outside

of the stern tube to refresh the "grey matter", please?

Thanks,

Maurice.

[Graeme Lock]

Hi Maurice. Shakti is still in the water, but I have attached a couple of pics. 

In the "Inside" one you can see the shaft, gland, hose, and a bit of the pinkish-looking copper tube aft of the hose.  There is no "nose" as per your description, but the tube extends a couple of inches past the F/G  into the hull to allow clamping the hose.

In the "Outside" one, taken some years ago during a previous slip, you can see the end of the cutlass, an inch or two of shaft, then the prop. The copper tube finishes flush with the deadwood.

I'm hoping I can use a reciprocating saw and make a couple of cuts lengthwise through the tube and then chisel it out. Then clean up the hole and push the new tube in, with some sort of goo (epoxy? .....TBC)  to fix it.in place. I should have time  before the epoxy sets to reinstall the shaft through the cutlass and onto the coupling, which will help align things. That way I shouldn't have a major alignment problem.  Of course I will need to finesse the alignment after she goes back in the water.

My best wishes to your grey matter and its memory functions.......

Cheers, Graeme

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[Mando C29]

Hello Graeme,

Thanks for the photos.

One method ( I think I did this with mine-20 years ago!) was once you have the tube clear and all the glands etc off

was to try and "crack" the copper pipe. If there is a small portion (which I think there is) of copper pipe clear in the boat, is to set up a puller. I did this with a length of M10 all thread rod and a small cross plate to fit across the copper pipe. On the outside you will need a similar setup with "stand offs" so that you are not putting any pressure around the cutless bearing area. If you send me your email I could send you a drawing!!

I found that with a reasonable amount of pressure on the all thread rod by winding the nut, it "cracked the seal " and by re making the pulling device so that it only was as wide as the external diameter of the pipe it came out quite easily. I want to emphasis that this worked for me but may not be the answer every time. The reciprocating saw approach would be (in my opinion) as the last resort however it may come down to that in the end.

The other challenge (love those corporate world words) is to get the shaft out as many times the coupling is rusted onto the shaft. If that happens, I've got a few ideas in that area.

You are quite right that you only need to play around with the alignment if it is needed so hopefully all is OK.

Keep me posted,

Cheers,

Maurice.

[Maeling]

There are times when you get lucky.  I made up a stern bearing puller years ago. it was under the house exactly where it should be.  10 minutes later, I've lost it!!

The main part is SS tube about 140  mm long, blanked off at one end with a 1/2" hole.

The other end has a rim to bear on the stern tube, then the bearing can be pulled into the puller tube.  I'll send a pic when find the darned thing, should be today.

Geoff.  When found, I can send it (Just the bell - you would just need the some 1/2"threaded rod and some big washers or plates.  End of a good story - it was on the back landing!  I'll send a pic to each of you before I lose it.

Geoff

[Maeling]

If the shaft is 1"" it will fit - and pull the old one out and the new one in. Will accommodate bearing up to 140mm long 

Geoff

[Maeling]

If you get the pic for this, I believe the C28 uses a 3/4" propshaft

Geoff Raebel

[lockie]

Thanks Geoff and Maurice, good to see the brains trust has lost nothing despite the advancing years.

Re "cracking" the tube, I will give this a try but it's possible the zincification has weakened it so that it might just crumble. But having said that, it might be ok anyway as it will just make the recip saw job that much easier. I still have the long threaded rod and bits and pieces from when I used it to press the new cutlass in a few years ago.

Re the shaft  (1)  - I've had it out multiple times over the years and always spray the fasteners and everything else with Lanox, so it all comes out easily. 

Re the shaft - (2) - it's 1" Geoff, having been re-engined with a 2GM way back before I got it.

Maurice , your response and encouragement are much appreciated: when I first saw the tube fall apart I had a a high-intensity "WTF" moment and started worrying about shipwright bills way above my pensioner pay-grade. But now I feel pretty confident that the damage will be a few days on the slip and not much by way of materials.

I will post a full report when I do the job.

Cheers, Graeme

[Mando C29]

Well done, Graeme. With all these things, knowledge is power. I suppose that  the real strength of

this site, thank you Geoff, is the sharing of past pains!!

Where I was in St Helens, I was able to slip the boat for long periods for zero cost. The down side was 

that there were very little help in the area, so most of my knowledge was gleaned the hard way.

On a completely different note, I am thinking of going to the Solomon Islands to visit the battle sites 

and would really like to speak to someone who may have been there recently to get the good oil.

Can anybody help? Sorry for using this site for personal business but I'm getting nowhere with travel agents.

Keep me posted,

Cheers,

Maurice.

[Maeling]

The bearing puller is still on my back landing so all must be good

Geoff

[Graeme Lock]

Whoops. As I understand it, C28's (and C29's?) were all fitted with copper stern tubes, so unless mine has been refitted with a brass or bronze tube, the cause obviously cannot be de-zincification. So why was the bit under the hose so fragile? Work hardening? A mystery to be resolved when I get the errant tube out.

Cheers, Graeme

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[Mando C29]

Hello Graeme,

I must admit I was a bit curious with your " dezincification" term when referring to copper!!

One explanation is that if electrolysis/corrosion has occurred between the copper and the shaft

the copper ends up tissue thin. On Mando, the tube ended up with lots of large holes in it!!

I think ( I'm no chemist),this is because pure copper is rarely used (too soft) but has additives in it to strength the tube.

As you said, Graeme, all will be revealed when the tube comes out.

Keep soldiering on,

Regards,

Maurice.

[Graeme Lock]

Thanks Maurice, sounds similar to my situation.

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[Graeme Lock]

Hi Maurice;

Hope you don't mind some more questions.

When you pulled the tube, did you pull it outwards (astern) or inwards (forward)? 

How long was the tube?

Thanks again, Graeme 

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[Maeling]

I pulled it aft through the sternpost.  With the helm to one side, I had lots of space to work.  My puller was necked down so that it bore on the lip of  copper tube
and the old bearing landed in the puller. Re installation was by using the puller to draw in the bearing.  I think I put a light smear of epoxy on the bearing to discourage it moving.

G

[Graeme Lock]

Thanks Geoff. I'm ok with the cutlass having done it 8 years/300 engine hours ago (and hoping I'll be able to reuse it). My question to Maurice concerns the stern tube.

Fortunately the bowels of the garage yielded a suitable length of 42mm ID steel tube (for the bell), a long enough bit of 12mm threaded rod plus nuts, and 1 1/4', 1 1/2' and 1 3/4' washers. All I had to make up were a few round wooden plugs with 1/2" holes to help keep the rod centred. Now I have to hope it will let me pull it out. But If not, plan B is to attack it with a mate's recip saw, collapse it inwards, then chisel the segments out.

Cheers, Graeme

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[Maeling]

You're on the right track My bell was 170 long 150 OD, Bell mouth ring,  4mm wall 8 MM long, 

I didn't add Washers, locknuts and threaded rod.

Send a couple of pics to help others

Regards

Geoff Raebel

[Mando C29]

Hello Graeme,

I replied to your question , however it didn't seem to get posted?

Did Geoff cut it off at the pass??

We seem to be in a 3 way split here?

Would you like me to answer your question or are you good?

Cheers,

Maurice,

[Graeme Lock]

Hi Maurice;

I saw your reply in the summary email  but for some reason I didn't get the direct copy. I'm thinking I might try extracting mine inwards, as I might not be able to make a good square end at the inboard end for the press to work on, due to the nature of the fracture. I'll probably have to take out the gearbox, but I've done that so many times I'm relaxed about it.

Geoff:   I'll take plenty of pix for the benefit of others.

Cheers, Graeme

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[Graeme Lock]

Happy days, the stern tube pulled right out under a pretty high force from the puller. The leftmost hole is where bits of the tube collapsed when I pulled off the hose from the gland. I'll post a description and more photos of what I did (including the replacement process) later, but for now I'd suggest considering replacement next time you slip. It's actually not much more work than replacing the cutlass. For the record, the tube is 38.5cm long.  Love is forever, but apparently copper is not.

Cheers, Graeme

[Mando C29]

Well done, Graeme.

[Maeling]

Keep us posted on your progress.

Geoff

[lockie]

Hi Geoff;

Shakti went back in the water on Monday after slipping Thursday arvo. I am delighted as it's been a great success - huge thanks to Maurice. I will sit down and write it all up in the next couple of days.

Cheers, Graeme