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Old 04-08-2013, 03:43   #1
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Stuffing box. Hot box.

I have just had the rear shaft replaced plus the stuffing box re packed with impregnated Teflon.
The prop end has been repacked as well, and both ends have their own grease feed.
Alignment is ok.
First outing at very low revs resulted in a very warm result. At times, I was unable to hold it for more than 5 seconds.
My experienced mechanic, who wasn't involved in this particular exercise, seems not overly concerned, saying it takes time for these things to bed in.
Well if so, how long? When is too long, too long?
Any thoughts from anyone who has experienced the same most welcome to comment.
I appreciate there have discussions on this before and have read extensively elsewhere.
Perhaps just need reassurance!
Thanks.
Peter.
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Old 04-08-2013, 08:27   #2
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Re: Stuffing box. Hot box.

Your mechanic sucks. What dangerous advice.

I just did this job last week. Read about it here:The world encompassed: Getting stuffed: a guide

The "settling in" part is correct, but not without adequate water flow. The customary process is to leave the box loose enough (and yet secured with the locking nut, of course) to have some arbitrary number of water drops per minute coursing through the packing.

Then you run the engine in gear. You feel or use a temperature gauge to determine that the water flow is adequate to cool the stuffing box.

Only then do you tighten down the box incrementally, until the flow is low enough to keep you happy about your bilges, but high enough so that the box never gets warmer than you can touch.

It's tricky and it's individual based on the water flow inside the log, the engine speed, the type of packing and lube and even the water temperature. The goal is (usually) about one or two drips per minute, maybe a few more under power. No drips or "too warm to touch" is burning up your packing and even damaging your shaft.

Back off that nut until you get drips and read the articles I've linked to in my post. I don't usually jump in with such a strong opinion on maintenance, but "just leave it" could wreck your shaft. People have lost their boats this way.
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Old 04-08-2013, 08:51   #3
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Re: Stuffing box. Hot box.

Great post, Alchemy.

Asked and answered.

Ann
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Old 04-08-2013, 08:58   #4
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Re: Stuffing box. Hot box.

Quote:
Originally Posted by S/V Alchemy View Post
Your mechanic sucks. What dangerous advice.

I just did this job last week. Read about it here:The world encompassed: Getting stuffed: a guide

The "settling in" part is correct, but not without adequate water flow. The customary process is to leave the box loose enough (and yet secured with the locking nut, of course) to have some arbitrary number of water drops per minute coursing through the packing.

Then you run the engine in gear. You feel or use a temperature gauge to determine that the water flow is adequate to cool the stuffing box.

Only then do you tighten down the box incrementally, until the flow is low enough to keep you happy about your bilges, but high enough so that the box never gets warmer than you can touch.

It's tricky and it's individual based on the water flow inside the log, the engine speed, the type of packing and lube and even the water temperature. The goal is (usually) about one or two drips per minute, maybe a few more under power. No drips or "too warm to touch" is burning up your packing and even damaging your shaft.

Back off that nut until you get drips and read the articles I've linked to in my post. I don't usually jump in with such a strong opinion on maintenance, but "just leave it" could wreck your shaft. People have lost their boats this way.
Alchemy - excellent post and thanks for sharing!
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Old 04-08-2013, 09:07   #5
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Re: Stuffing box. Hot box.

With the teflon impregnated packing, you may be able to back the compression nut off until it is warm enough to hold without having any drips.
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Old 04-08-2013, 09:54   #6
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Re: Stuffing box. Hot box.

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Originally Posted by donradcliffe View Post
With the teflon impregnated packing, you may be able to back the compression nut off until it is warm enough to hold without having any drips.
True. My point was that it is very much something you tweak to get right in a balance between drips and warmth...with too many drips, but a cool stuffing box being preferable, if a little counter-intuitive, perhaps, to the alternative of a stuffing box that doubles as a toaster. If you can nail "not warm and nearly zero drips", more power to you, although I like a few drips because I can tell from what I find in the bilges over X number of unattended days whether I need to make adjustments. We are talking half-a-cup or a couple of sponges...not something that would ever activate the bilge pump.

The teflon impregnated packing will, in my experience, tolerate more abuse than the tradition packing you have to grease up. But pulling the same out of the cup last week made me reconsider "convenience"

Which is why I've gone back to old-school packing which I smear myself (in a strong light!). I would rather tweak and get the drip/warmth contrast correct than just half-ass it, and the old "you-grease-it" packing demands a higher grade of tweak.
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Old 04-08-2013, 16:31   #7
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Re: Stuffing box. Hot box.

Yes thanks Alchemy. Great reply. Checked and read your blog site. Well written.

I am not too fussed about dripping. I have a 1903 hull which always has the odd leak so a few drops of warm water is no drama.

I will recheck alignment. A cursory check showed that it was ok.
I have a 2 section shaft. The prop to through hull section is all new.
The section between there and the gearbox is supported by 2 bearings.

Unfortunately she was on the hard for a month due to poor weather slowing down work but had been back in the water for 6 days before our little cruise.
These old boats do take time to settle.
She is a 36 footer.
Thanks to all contributors. I know it is a subject that has been done to death (and will continue to flogged), but appreciate people taking the trouble to respond.

Peter.
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Old 04-08-2013, 22:11   #8
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Re: Stuffing box. Hot box.

By two-section shaft, do you mean that it has a universal joint, or some kind of thrust bearing? I ask because that might add either extra wear in the form of vibration or extra movement of the shaft if it's unsupported, in which case alignment would be more critical even than with a typical keyway and coupler and grub screw arrangement forward of the stuffing box.

Wooden boats are always a touch damp. I agree that whatever your setup, you can stand to back off the stuffing box to assure flow, let the boat itself settle, and then do your alignments and your stuffing box adjustments.

This thread made me go down and back off my own newly packed stuffing box a quarter-turn, until I felt a couple of drips per minute. After I run the engine a few hours, I will likely fiddle with it again.

It is the nature of the thing, I've found.
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Old 05-08-2013, 03:33   #9
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Re: Stuffing box. Hot box.

Hi Alchemy.
The setup is:
Gearbox end attaches to a flexi coupling. 5/6 rubber 'knobs' set into cups; then a 1.75m ( guesstimate) shaft supported by 2 bearings; then a coupling; then the stuffing box with the prop end shaft being at least 2m long.
I'm not high on the correct terms so I hope I make sense.
The most "unsupported" section is the stuffing box to prop section; the shaft log section.
Not much I can do about that.
Going up tomorrow to have another look at it.
Thanks for your interest.
Peter.
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