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Go Back   SailNet Community > On Board > Gear & Maintenance > Send packing the stuffing gland..
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Topic Review (Newest First)
03-27-2013 06:49 PM
fallard
Re: Send packing the stuffing gland..

The nice thing about the PSS shaft seal is that it provides "wiggle" room if everything doesn't line up perfectly. The photo here shows my PSS shaft seal after replacing the bellows. The engine-cutless bearing alignment was fine, but the shaft log wasn't precisely aligned, as evident from the bend in the bellows. Nonetheless, the seal works perfectly.



This job was done when my 1990 boat was 17 years old. Only the bellows, o-rings, and hose clamps were changed. The (dark gray) graphite stator, which is captured by the bellows, is original, as is the SS rotor.

The electrical tape was placed when the rotor was just contacting the graphite stator. Per instructions, the rotor was then moved 3/4" to compress the bellows and then fixed in position with 2 set screws, one of which is showing. The "V" mark points to the more polished surface of the rotor.

We are now coming up to 23 years, with over 1000 hours on the engine and a lot longer to go before expecting to replace anything. Still dripless (except when I churn up silt on occasion at low tide--and even then it doesn't spit enough to require pumping.)
03-27-2013 05:29 PM
Tubsmacker
Re: Send packing the stuffing gland..

Hi Eherlihy and thanks for taking the time to consider my problem.

I had considered that the shaft could have been bent during the first incident but couldn't see any evidence of this when it was inspected albeit in situ.

The stuffing box shouldn't get close to the stern tube as its connected with a set of clips to the 5 inch rubber tube that slides on to the stern tube. However I will check that.

There may well be an issue with a bent shaft though so I think I will pull that and replace if required. I still don't know if I feel I could ever trust this set again though.

As for the bilge pump I replaced/fitted a huge one with a float switch before the last fiasco. but my emergency pumps stopped the water getting down that far this time.
I have to say though that last time this happened the big bilge pump did kick in but the pump out rate seemed wholly less than the claimed figure when I purchased it. possibly due to height from bilge to outlet on my high freeboard boat. That's why I have the standby pumps to hand.
03-27-2013 03:36 PM
eherlihy
Re: Send packing the stuffing gland..

Here are my 2˘;

I suspect that when Tubsmacker experienced the original problem that several things that may have happened;
  1. the broken motor mounts may have caused (or been caused by) the prop shaft to become untrue (bent).
  2. a bent prop shaft will have caused the stuffing box to chafe the stern tube so that it may now be tapered.
  3. tightening the hose clamps with a tapered stern tube will push the stuffing box hose forward.
  4. if the shaft is still untrue, this will also contribute to the stuffing box hose moving forward.
  5. If there is any grease present on the stern tube, it would exacerbate the slippage.

I advise looking closely at the shaft while the boat is hauled, and be prepared to replace it. I would also look closely at the stern tube (shaft log), and be prepared with epoxy and cloth to effect a repair here.

While the boat is hauled, I would also take this opportunity to add a bilge pump, and the requisite plumbing, which is hard wired to the largest of your battery banks.

Good luck!
03-27-2013 01:26 PM
Tubsmacker
Re: Send packing the stuffing gland..

Oh and the shaft etc never ran hot but it can slide Fwd which is not possible on the PSS system particularly if you put a shaft collar on
03-27-2013 01:24 PM
Tubsmacker
Re: Send packing the stuffing gland..

Well after It has come off twice. Ideal isn't a word I'd use to describe it right now!
I checked the clamps which are doubled up 3 months ago. Engine mounts are new so that cant move a lot. Dunno yet I will try to investigate more now I am in the yard.

One point I would make is that when I researched using Teflon braid in the stuffing box. The instructions specifically say NOT to use grease as a lubricant.
So maybe you might want to check that out with your supplier as well.
03-27-2013 12:51 PM
copacabana
Re: Send packing the stuffing gland..

Are the hose clamps properly tightened (and doubled up if there's room)? Has the motor shifted and pulled the hose off or misaligned it? I can't imagine the hose letting go unless the clamps were loose or something forced it. I think the system you have is pretty much ideal and, with regular checking of the hose clamps, should give you trouble-free service. I have the same setup: teflon stuffing and a greaser on the gland. I tighten my stuffing just enough so it doesn't drip. I give the grease gun a little turn every 25 hours or so to force a little more grease into the gland. The grease protects the shaft and keeps it running cool and dry (no drips). After a run, put your hand on the stuffing box to make sure it isn't running hot. Not sure a dripless PPS system will be any more reliable.
03-27-2013 12:14 PM
Tubsmacker
Re: Send packing the stuffing gland..

Yesterday I lifted out into the boatyard here in Portugal after a fraught 18 hours nursing a leak from the stern tube fitting. I think its Vetus and the it's the second potential sinking failure I have sustained in 3 years.

The original problem occurred during the short journey from my mooring to the boat yard. As I went below to turn off the engine, I noticed the cabin sole bubbling under rising water. When I opened the engine bay, it looked like the inside of a washing machine. So I umm .... shut it again quickly. It's kind of like when I used to fly small planes. The advice goes..If you have an engine failure at night, turn on your landing lights. If you don't like what you see......Turn them off again!

The Stern tube rubber is held on with 2 hose clips and the tube had come off.
Inspection suggested that the two rear engine mounts had sagged/failed and allowed the rear of the engine to drop down so that the shaft came into contact with the rubber hose and made it come off.

Solution was to fit new engine mounts and align. fit new rubber with bigger hose clips on both ends. I replaced the stuffing with that black Teflon stuff.
Re-launched boat 1 year ago. took some time to get the new packing to settle in as sometimes the drip would be too much and still leak when the prop wasn't turning and some times there was no drip at all when not moving or almost none when moving. I figured that in the end I would probably put another ring of stuffing in.

During the year I noticed that sometimes when I engaged gear forward the drip would stop and stay stopped so I made a habit of giving a little forward power just before shutting down. Two days ago I ran the engine to charge my batteries. when I stopped the engine I noticed that the previously dry engine bay now had water in it and was still coming in a bit too much so I employed the forward gear principle. Hmmm bad idea. When I shut the engine down I could hear the water coming in fast and saw it rising. I quickly deployed emergency pump no1 into the engine bay. It's a Rule submersible pump runs of the standard cigar lighter supply. I recommend one of these as its a fast way of making a start. Next In deployed he generator and emergency pump no 2 which is a Karcher garden pump. During this my partner was making access possible to the hatch that would allow me to get to the stern gland. but at least by this time we had the rising water under control.

On inspection it appeared that the rubber hose had rotated 180 deg and moved forward as there is no collar on the shaft forward of the stuffing box.
I did consider fitting one of these after the last fiasco but was advised that it might score the shaft. (Um would that matter there?)
anyhow so the upshot is that the rubber hose was on the cusp of coming off and water was coming in at the rear (aft) of the stern tube rubber and I was able to push it back on. However, when I tried to tighten the clips it got worse each time I tried. I took stock. It was 5 hours before high water (at night) and I had a long time to wait before I could get a haul out. I figured that if I continued to try and fit it back more securely it might come off completely.
I therefore elected to leave it trickling in at a 1/2 litre a minute which was better than 10 litres a minute I had not-so-long-ago. We took shifts and pumped with the rule pump alone for 2 mins or so every 35 mins. for the next 18 hours. I reckoned if I put the boat into gear then the tube would deffo come off so I arranged a tow to the yard about a mile away. Of course we had 30Kt winds to make things more fraught.

So now I am here in the yard, wondering If I can find a solution here to my problem. I have looked at the PSS seal video and think that it might be the way to go. Not least of which because the metal disc screws into the shaft a little and I could,would, WILL fit a shaft collar forward of that.
If those O rings ever failed it could be bad I agree but it would be possible to make a rubber washer that butted up to that thing between it and the shaft collar perhaps?

My original stuffing box greaser actually fitted to the stern tube and I was advised to lock it off so grease couldn't get into the rubber hose. That's why I fitted the Teflon braid. But I wonder if any residual grease got pushed by water pressure to loosen the grip of the hose clips holding the tube to the stern fitting. The stuffing box is bronze about 4 inches long and has a knurled hand tightening collar with a locking tab. (Poss Vetus?)
The rubber tube says Vetus 30 on it.

Sorry for the enourmous post but would be grateful for any suggestions as to why it came off as well as what would be the best solution now.
03-23-2013 06:15 PM
zeehag
Re: Send packing the stuffing gland..

my stuffing bos, sans stuffing, only allows into boat enough water to empty every 2 hours to the count of exactly 45 seconds every 2 hours for a 800gph bilge pump. i can let 12 hours go by with only 120 seconds of pumping--dont ask me --i only count the seconds, i dont do the math.....with teflon stuffing, there was a huge improvement, but the alignment..yada yada quack quack.....
we will be designing a specific stuffing box for this boat as we go . i have a flanged unit that buck algonquin denies knowledge of and stares never saw ever in life one like this....ok. i own a formosa..we fabricate....we may even remember to post pix when we finish the design and install it.
we will add a third bilge pump and a manual one also. so far, i have travelled 2000 miles with my 'unknown to buck algonquin and man' flanged unit--with modifications, perhaps long enough to find a replacement. LOL or make one.

hecho en chine......rodlmao.
03-23-2013 05:50 PM
BELLATRIX1965
Re: Send packing the stuffing gland..

Quote:
Originally Posted by Sabreman View Post
After replacing a shaft in 1988 and again in 1992, we replaced out Sabre 28's stuffing box with a PSS shaft seal. When we sold the boat in 2005, it was still going strong.

When we bought Victoria, I replaced the stuffing box in 2006 and have had no issues. It's maintenance free and easy to install. I check it each spring before launching and periodically throughout the season.

IMO, generally speaking, things just don't "give out", there are usually warning signs. Stuffing boxes have sunk their share of boats, so they are by no means "safer" than anything else. But to me, ANY drip is bad.... water belongs outside the boat.
What Sabreman said!!! I was a professional marine engineer for 30 years (licensed Chief Engineer), and I can tell you that, properly installed, a mechanical seal is the way to go (PSS). I installed mine in 2007, and will be overhauling the seal before splash day this year (the overhaul kit includes the elastomer bellows, set screws and o-rings). Note that the manufacturer recommends not exceeding a 6 year interval between overhauls. This is probably over-cautious, but better safe than sorry.

Granted, you have to break the coupling and shift the prop shaft to install or maintain one of these. I installed a small water supply line teed off my raw water system to feed flushing water through the seal. This prevents "dry running" - which can burn out a mechanical seal in short order - and it constantly flushes clean water across the seal faces. This seal works well, and I can highly recommend it. Some items to watch for:
a) Make sure that the shaft is polished clean before installation, and there are no sharp edges on the shaft which might cut the O-rings.
b) Lightly lubricate the shaft before installation. (for the o-rings)
c) DO NOT touch or lubricate the seal faces before or during installation.
d) ALWAYS use new SS set screws when assembling or re-assembling the seal - they are only good for one use!
03-23-2013 03:11 PM
eherlihy
Re: Send packing the stuffing gland..

I installed a PSS before the beginning of last season. If you are interested, you can read about it here: http://www.sailnet.com/forums/gear-m...-overhaul.html

So far, I am happy with the installation. I have not had a drop of water infiltrate the hull since.

The "gotchas" are:
  • the set screws are meant to be used once. Many yard monkeys don't get this.
  • the "O" rings can be damaged by grease/oil. You can only lubricate them with dish soap, and you should ensure that there are no burrs on the shaft that could damage them during the install.
  • PSS should include a redundant collar (they don't), because of the potential for failure if the installer damages the set screws. If you go with a PSS, you should find and install a collar, as a backup.
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