Stern tube getting really hot

[Mitchellmoxo]

Hi Richard,

 

Do you mean something like a CV joint? If so then no its a fixed fitting just 2 plates bolted together with some sort of spacer in between.

 

Regards

[RLWP]

Then you need to realign the engine and gearbox too. Start by taking the bolts out that join the plates and see what happens. My guess is that you'll find the plates no longer sit flat to each other

 

This makes even more sense - the bottom of the hull carrying the engine bearers has moved misaligning the sterngear

 

Richard

[Timleech]

Hi Richard,

 

Do you mean something like a CV joint? If so then no its a fixed fitting just 2 plates bolted together with some sort of spacer in between.

 

Regards

 

Is the spacer white-ish, synthetic material?

 

If so, it'll be an R&D coupling which is poor man's flexible coupling. Theydo allow for a bit of angular misalignment, but very little axial misalignment.

 

Tim

[bizzard]

Hi Richard,

 

Do you mean something like a CV joint? If so then no its a fixed fitting just 2 plates bolted together with some sort of spacer in between.

 

Regards

Your boat looks like a Harborough marine, in which case it probably has the Lister set up of engine, gearbox and flexible coupling, which looks like a wheel barrow tyre trapped between plates, these are excellent. They often fitted the beefy Dodge thrust block as depicted by Ray T.

Edited March 1, 2015 by bizzard

[Bee]

These comments need to be treated with some caution, I feel.

 

Many marine gearboxes are actually designed on the assumption they will be taking the thrust of the propeller, and some older gearboxes actually must take the thrust of the propeller. If you look at the manuals for such gearboxes, if you wished to run with a thrust bearing in addition to the one in the gearbox, then the gearbox had to have it's bearings changed to a different type.

 

So, as in all things like this, it is not quite as obvious as it may initially seem, and each case may have different considerations.

[/quote Yes, you are right, some of the older boxes do need thrust. Its really the use of plummer blocks as thrust bearings I was thinking of. So far as gearboxes taking thrust are concerned, yes they maybe designed to but I would still prefer to have the thrust taken by a bearing fixed to the hull rather than transferred to (possibly rubber) engine mounts through a flexible coupling. I am not too sure about thrust on flexi couplings, I know that some flexi couplings don't like being pushed and pulled, I got through a couple of tyres on a Fennerflex coupling before I realised what was happening, I swapped it for a solid coupling and that same Fenner is now installed on our boat with a Python drive as a thrust bearing and the Fenner just absorbs the wobble from the rubber mounted engine.

[Mitchellmoxo]

The spacer is a yellow and of a plastic type material? Is that a flexible coupling?

 

I have managed to find a pic on the Internet which looks to be the same as mine. Apart from mine is yellow in the picture it is white

[nicknorman]

The spacer is a yellow and of a plastic type material? Is that a flexible coupling?

I have managed to find a pic on the Internet which looks to be the same as mine. Apart from mine is yellow in the picture it is white

Yes it is, but it's only designed to take a very slight angular misalignment and won't take any parallel misalignment. So to be honest, it's best not to think of it as a flexible coupling - proper alignment is still critical. Of course you may have the engine flexibly mounted, in which case that can absorb some misalignment. On our boat, with flexible engine mounts and a centraflex coupling (which is a larger version of what you have) when I corrected a very slight misalignment it made for a significant reduction in vibration. Significant as in from not very much, to virtually zero.

[Radiomariner]

I have been looking at the OP's original photo. I notice that there are splashes of water in the stern gland yet the tube seems o be dry and appears discoloured. The OP did say it was stern tube that was heating not gland, and from the picture I assume that is so. It sounds very much to me like old hardened packing has wedged between shaft and tube, or the shaft has bent as others have suggested. A bent shaft (or perhaps a damaged stern tube) would in my opinion cause a notable amount of vibration and noise (especially as there is a plummer block). The OP did not mention this, so my guess is old packing down the tube. (Or some foreign object getting in there during maintenance

Edited March 1, 2015 by Radiomariner

[bizzard]

If it is a Harborough boat, which I think it is, it almost certainly would originally have had a solid mounted Lister SR2 or 3, an LM100 gearbox or more likely a LH150, usually coupled to the Fenner tyre style flexible coupling, and again often with a Dodge Fenner thrust block, but not always and Lister or Lister recommended stern tube assembly. If so, that plastic R&D type coupling is a later adaptation. Originally the engine would have had the flange fitting Burgess silencer too.

 

PS All supplied by Lister as a package when the boat was built.

Edited March 1, 2015 by bizzard

[Albion]

I have been looking at the OP's original photo. I notice that there are splashes of water in the stern gland yet the tube seems o be dry and appears discoloured. The OP did say it was stern tube that was heating not gland, and from the picture I assume that is so. It sounds very much to me like old hardened packing has wedged between shaft and tube, or the shaft has bent as others have suggested. A bent shaft (or perhaps a damaged stern tube) would in my opinion cause a notable amount of vibration and noise (especially as there is a plummer block). The OP did not mention this, so my guess is old packing down the tube. (Or some foreign object getting in there during maintenance

Isn't that because in post #1 the OP said that they had had to pour water over it and that the stern tube overheating had caused the water to boil off immediately? Surely, after a dousing in water, you would see water droplets in some places and discoloured, over-heated aspects elsewhere?

Roger

[RLWP]

There are instructions for aligning R&D couplings here: http://www.randdmarine.com/flexiblescinst.asp

 

Richard

[cereal tiller]

I have been looking at the OP's original photo. I notice that there are splashes of water in the stern gland yet the tube seems o be dry and appears discoloured. The OP did say it was stern tube that was heating not gland, and from the picture I assume that is so. It sounds very much to me like old hardened packing has wedged between shaft and tube, or the shaft has bent as others have suggested. A bent shaft (or perhaps a damaged stern tube) would in my opinion cause a notable amount of vibration and noise (especially as there is a plummer block). The OP did not mention this, so my guess is old packing down the tube. (Or some foreign object getting in there during maintenance

Yes,quite possible that dust and metal particles may have found their way into the stern tube and formed what old fashioned Plumbers call a 'Rust Joint'.

Once the boat was re-floated any trapped rust would expand and limit water supply to the Stern tube.

 

The Greaser is primarily for the purpose of lubricating the Yellow metal Bearing which centralises the shaft and is nothing to do with lubricating the gland packing.

 

CT

[bizzard]

I had a 40' Harborough marine and I had to overplate the stern end almost the same as the boat in question. No distortion of the hulls structure was caused though and the drive line was still in perfect alignment when refloated. But there are many variables. If the boat docks plinths are not square and level or the boat is not chocked up on land square and perfectly level the hull can distort and then remain distorted after welding and when back in the water and suddenly cause the puzzling misalignment trouble.

[Timleech]

 

The Greaser is primarily for the purpose of lubricating the Yellow metal Bearing which centralises the shaft and is nothing to do with lubricating the gland packing.

 

CT

 

I don't agree with that last comment. It serves both purposes.

Larger sterngear often has two feeds, one to the stern bearing and one to the gland.

 

Tim

[cereal tiller]

 

I don't agree with that last comment. It serves both purposes.

Larger sterngear often has two feeds, one to the stern bearing and one to the gland.

 

Tim

And lots of commercial use Sterntubes have seals at each end and are filled with oil.

 

Most Canal boats have Shafts that are relatively short so water is an adequate lubricant as the shafts are usually stainless steel and the bearing is yellow metal.

The effect of grease being pumped into the Tube also resists Grit finding it's way into the bearing face which is placed ahead of the stuffing box

 

CT

[Timleech]

And lots of commercial use Sterntubes have seals at each end and are filled with oil.

That's exactly how the sterngear on my own boat is arranged (the boat is only 35' long, BTW)

 

Most Canal boats have Shafts that are relatively short so water is an adequate lubricant as the shafts are usually stainless steel and the bearing is yellow metal.

The effect of grease being pumped into the Tube also resists Grit finding it's way into the bearing face which is placed ahead of the stuffing box

 

CT

Agree about the keeping out of grit, but still contend that one major purpose of the grease is to lubricate the gland and to help it to seal.

 

Older working narrowboat sterngear generally had a very long gland, maybe as much as 6" long, and a very long bearing (I've re-bushed bearings about 12" long). The only deliberate lubrication was a small grease cup immediately behind the gland, which had not a hope in hell of providing enough grease to keep the bearing lubricated, its purpose was to keep the gland lubricated and sealed. Water is indeed the main lubricant for that style of sterngear. Some later working boat sterngear has a second greaser, feeding direct to the bearing.

Modern narrowboat sterngear has much shorter glands and bearings, and runs at higher speeds, so lubrication of the bearing becomes more critical. Water is a fair lubricant at low speeds and low pressures.

 

 

There are instructions for aligning R&D couplings here: http://www.randdmarine.com/flexiblescinst.asp

 

Richard

I've never really trusted that method. Much better, if physically possible, to remove the R&D and bring the flanges together, and do the job properly.

 

Tim

Edited March 1, 2015 by Timleech

[RLWP]

I agree.

 

Richard

[Mitchellmoxo]

The next step for me is to check the R&D coupling for proper alignment, then if that doesnt do anything then check plummer bearing, then the stern packing if not.

 

Many thanks for all the advice given by everyone it really is appreciated.

[RLWP]

No problem, it's what we do here

 

Richard

[nb Innisfree]

I've always kept our stern gland tight enough to stop any water drips, this ensures nearly all the grease takes the path of least resistance and goes rearwards to the bearing, though a very small amount does escape via the stern gland which is beneficial I think. Combined with our Python Drive the stern gland has kept the bilge dry for over 3.5 thousand hours with no adjustment needed (though I haven't been able to resist the odd fiddle or two!)

[Radiomariner]

Isn't that because in post #1 the OP said that they had had to pour water over it and that the stern tube overheating had caused the water to boil off immediately? Surely, after a dousing in water, you would see water droplets in some places and discoloured, over-heated aspects elsewhere?

Roger

That was exactly my point. The gland area still had water droplets. The stern tube was bone dry. Because of the water droplets I assumed the photo was taken shortly after it was "doused"

 

Overheated stern tubes was one of our biggest nightmares at sea because if you couldn't fix it the next step was to call the tugs!

[Neil2]

Assuming the problem is distortion of the hull caused by overplating it is a little ironic that this was the much lauded job on which there is a long running thread on the forum.

 

Maybe I'm displaying my ignorance here but it never occurred to me that the heat generated by the overplating process could cause enough distortion to put an engine out of alignment,

 

So, am I being naive and should anyone having hull repairs carried out at the blunt end be wary of this sort of thing?

 

And is the fact that it was MIG welded relevant?

[Martin Kedian]

I have been away for a few days and just picked up this thread my understanding was that there was an issue with the stern tube getting hot on its way to us from Milton Keynes and I am sure that the boat was correctly aligned prior to replating also we covered the boss so as to stop any incursions by grit etc as we worked close by the prop turned freely on completion and the heat produced would not have disturbed the original alignment of the shaft it was the same after the work was completed as before

[Tony Dunkley]

I think there's a good chance that either some thin wire or fishing line may have worked it's way up the outer bearing into the tube. In the photo in the OP, the tube looks to have been hotter than either the steel bush at the outer end or the stuffing box.

[African Queen]

I'm, or at least I seem to be having overheating problems with my packing gland. I gets too hot to touch after about 15 - 20 mins of moderate use.

The prop turns by hand when cold, not tried it when hot yet. Advice about the make and model might reveal a further line of enquiry with the manufacturer?

Picture attached.