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Old 01-14-2010, 09:28 AM   #1
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stuffing box replacment

I have an old marine trader 34'* I would like to replace the stuffing box with a pss seal system* This boat has a stern tube with the stuffing box threaded on the end and bolted to a crossmember,*and not much propshaft exposed* Is it possible to refit to a dripless system?
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Old 01-14-2010, 05:11 PM   #2
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RE: stuffing box replacment

Hiya Motion,
***I would suggest, unless the old stuffing box system is damaged, to keep it.* Failure of the bellows on a PSS system could very well sink your boat.*
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Old 01-14-2010, 05:48 PM   #3
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RE: stuffing box replacment

Quote:
RT Firefly wrote:

I would suggest, unless the old stuffing box system is damaged, to keep it.* Failure of the bellows on a PSS system could very well sink your boat.
I'll second that. I have installed a couple of them but really never have been able to feel all cozy about the things. They just aren't as "bulletproof" as I believe a seal should be and there is no second chance.

Larger versions of mechanical shaft seals usually incorporate an inflatable bladder to seal the shaft when the seal is damaged or fails.
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Old 01-15-2010, 04:37 AM   #4
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RE: stuffing box replacment

The PSS setup is far to dangerous and has been replaced with more modern stuffing material.

Duramax and its competition are far superior , function with Zero effort (or danger) with no dripping into the boat.

And no mandatory shaft removal every few years to replace bellows.
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Old 01-15-2010, 07:13 AM   #5
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stuffing box replacment

I agree that retrofitting an older standard packing stern tube to PSS is questionable. But using the word "dangerous," as FF has done, to describe PSS systems is a stretch. A stern tube and shaft setup*is like any thru hull - it must be designed right and inspected regularly. Many do not like active stabilizers because they are a big thru hull etc etc. And is your exhaust system designed to live through a rat or muskrat brunch etc etc. And can each and every one of your thru hulls take a 250# load for 30 minutes etc etc*

But this is 2010. There are fly by wire jumbo jets, glass panels and GPS units in aircarft -*that many yet*decry. And even more shocking, the most successful blue water boat manufacturer, Nordhavn, uses PSS systems. Their big *75 and 82 footers use PSS on the 3-1/2 to 4" shafts and nary has one yet sunk due to this "dangerous" situation. Let alone the smaller Nordhavn vessels running around the world that have PSS systems. My PSS dripless systems are working fine and get inspected for temp and leaks every hour I'm cruising. I'd guess far moreso than any standard system gets checked in*most vessels.

So FF and rickB, even though you are both in agreement on this one, the boating world has passed*you by.

-- Edited by sunchaser on Friday 15th of January 2010 08:16:27 AM
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Old 01-15-2010, 08:21 AM   #6
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stuffing box replacment

Quote:
sunchaser wrote:

the boating world has passed*you by.

*
Hardly.

I work with the latest and best world class yachts where money is*barely an issue when it comes to the machinery installation.*None of these boats use a seal that cannot be closed off, either by an inflateable bladder or by clamping down on some other type of emergency seal.

Show me another*item below the waterline on a boat where the only thing between the sea and thee is a very thin and very flexible rubber bellows with no way to stop flooding when it fails.

"My PSS dripless systems are working fine and get inspected for temp and leaks every hour I'm cruising. I'd guess far moreso than any standard system gets checked in*most vessels."

That's because other systems can be trusted to behave themselves and don't require that much labor.


-- Edited by RickB on Friday 15th of January 2010 09:25:10 AM
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Old 01-15-2010, 09:53 AM   #7
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stuffing box replacment

Point made RickB. Note I did not say you are wrong. However, with 1000s of dripless systems out there and more coming, the trend is obvious and well established. And with the mother hens of AYBC continuing to issue guidelines, dripless get a passing mark. It has been some time, but I well recall the article Steve D wrote on packing systems that this Forum's small boat members use. Passive systems hardly get a free pass.

To me "dangerous" is "thin rubber" connected to*100,000s of stern drive bellows, numerous IPS drives, thru hulls for heads, macerators, cooling water*intake, ACs,*washdowns, stabilizers*etc. that hardly ever get inspected until they start*leaking. Just the thought of all these "dangerous" hoses*is enough to make one paranoid --------------

-- Edited by sunchaser on Friday 15th of January 2010 11:02:21 AM
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Old 01-15-2010, 10:39 AM   #8
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RE: stuffing box replacment

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Just the thought of all these "dangerous" hoses*is enough to make one paranoid --------------

On a properly built boat all those "dangerous hoses" are connected to seacocks that can be closed if there is a problem with the hose. On our boat we leave all the seacocks except the two engine raw water seacocks closed unless we are actually using the boat.* Dripless shaft seals are fine (although I don't understand why so many people are so deathly terrified of a bit of water in the bilge) but like any higher-tech system, they require more care and more attention.*

In the eleven years we've owned our boat the flax-packed shaft logs have required adjustment only a couple of times and have only had to be re-packed once and that was only because we had the shafts out of the boat so we figured might as well do it.* They don't drip when the shafts are not turning and they barely drip when they are.* They run dead cold.* I glance at them when I do an engine room check, which is only once per day's run.

Having to climb down into the engine room religiously every hour is not the way I want to go boating.* If the equipment in there is so unreliable or prone to problems that it requires that kind of surveillance, it's not the kind of equipment I would want to have.

*
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Old 01-15-2010, 12:14 PM   #9
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stuffing box replacment

Marin* - Have you ever owned a stern drive?* There are no shut off valves on the 3 bellows that each have. Again, there are 100,000s of these out there. And on the new GB IPS systems, where is the shut off valve?* If you are not on your boat to close the thru hull when*the macerator line ruptures, the boat sinks.* I picked on the macerator because it is a PD pump and quite capable of blowing out a sh---y old line.

My dock mates Krogen sank at the dock 6 years ago with closed through hulls. Bonding system went awry. Quite simply there are untold ways for your boat to go down. The most common (non hurricane)according to the insurers - drain plugs and hoses connected to the water system under pressure while the owner is on the boat (or out to dinner)***

It is near impossible to buy a newer boat that does not have a dripless system. I will give you a $100*for every owner who has taken out dripless if you give me $50 for every owner who has installed dripless.

So what we really have here is old boats vs new boats. The train left the station 50 years ago on bellows below the water line. They only have gotten better.


-- Edited by sunchaser on Friday 15th of January 2010 01:21:57 PM
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Old 01-15-2010, 02:32 PM   #10
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RE: stuffing box replacment

Quote:
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Marin* - Have you ever owned a stern drive?
No, but I have met five people that I can remember who had stern drives and had the boat sink, or start to sink, because of a failed gasket or boot.

I'm sure the technology has come a long way.* But just because dripless systems are becoming the norm on newer boats does not automatically mean that standard packed glands are bad.* They're fine, and from your description they take a hell of a lot less oversight than the dripless system.* A system that requires me to crawl down into the engine room every hour to make sure it's okay doesn't sound like much of an advancement to me, no matter how snazzy the technology is.

I'll take our ancient, low-tech, never-worry-about them flax-packed glands any day over some fancy system that is so potentially trouble-prone I have to keep checking on it whenever I'm running the boat.* That's a step backward in my book.

*
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Old 01-15-2010, 06:14 PM   #11
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RE: stuffing box replacment

Marin:

I have owned stern drives for the past 40 years. Not a sinker in the group. Of course I do a little bellows replacement now and then. The Volvo*boot? That went out in the 70s.

I take sandwiches into my ER and wait for my wife to buzz me back to the helm. She can't understand why I spend all that time watching PSS bellows for leaks. I tell her it is a "dangerous" situation and I'm trying to prevent Armageddon. I told her I want Gore and she says "So why did you vote for BUSH?"

Anyway, I'm in Santiago and bored tonight so thought I'd have some fun. Off to Lima in the AM

Lo siento y adios.
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Old 01-15-2010, 06:35 PM   #12
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stuffing box replacment

Quote:
sunchaser wrote:

I take sandwiches into my ER and wait for my wife to buzz me back to the helm. She can't understand why I spend all that time watching PSS bellows for leaks.
Sounds like a great excuse to get more goodies for the boat.* What you need is a pair (I assume you have a twin) of high-definition color video cameras mounted so they look at the PSS seals with the appropriate lighting.* Then you need a*big 1080p**LCD HD screen*display the camera shots*in a split screen.** Don't get a plasma screen because they are not as sharp as an LCD screen.**And you have to have HD because that's the only way to get sufficient detail to see the splits in the seals developing.*

Then, with the LCD screen mounted where it can be seen from the helm, you and your wife can monitor the health of the shaft seals on a full-time basis from the comfort of a nice seat.* They say two pairs of eyes are better than one.

-- Edited by Marin on Friday 15th of January 2010 07:40:44 PM
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Old 01-15-2010, 07:05 PM   #13
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stuffing box replacment

Quote:
sunchaser wrote:

Point made RickB. Note I did not say you are wrong. However, with 1000s of dripless systems out there and more coming, the trend is obvious and well established.*
And I never called them "dangerous" but I don't think they are worth retrofitting either. As far as Nordhavn using them, they are cheaper than the better made units and they are probably familiar to the demographic that buys Nordhavns because they advertise in all the magazines.

The seals we use on larger yachts are similar, they use a mechanical seal, hardened metal on ceramic elements, but the rubber* bellows is short and thick and there is an inflatable bladder internally that will seal the shaft if the seal or bellows fails. These are heavy duty, reliable, and provide the degree of protection that the owners of those boats demand.

Just like a valve on a hull penetration, and two hose clamps, having a second layer of isolation is only good practice. To remove a nearly bullet[proof system* just to follow the current fashion is silly in my book. How do you justify the cost and increase in labor, much less give up the reliability of a packed seal?

If I woke up one morning desperate to get rid of a stuffing box on a small boat I would consider the Manecraft "deep sea seal" type as it is much sturdier and incorporates a safety seal to prevent uncontrolled flooding. It is what the ones advertising in PMM pretend to be.

And as far as I/O bellows go ... there is no shortage of flooding/sinking stories related to them. I have seen two and I don't even hang out around the things.

*

*


-- Edited by RickB on Friday 15th of January 2010 08:07:15 PM

-- Edited by RickB on Friday 15th of January 2010 08:07:58 PM
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Old 01-15-2010, 08:20 PM   #14
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stuffing box replacment

Had an interesting conversation about three years ago*with a design engineer at a local marine fabricator that makes radar towers (my reason for being there), driveline components, and sells and distributes other driveline components like dripless shaft seals (PSS).

I asked him what the advantages were of dripless shaft seals. He asked me if we had them on our boat. I said, no. He asked me if we were considering changing over to a dripless system. I said I didn't really know anything about them so didn't know what advantage it offered. His next comment was an interesting take on today's boat buyers (by which I assumed he meant new-boat buyers).

He said to not bother spending money on dripless seals. He said the only advantage they offer over a conventional packing gland is that they don't drip. He said the reason their company carried PSS seals and sold a lot of them was that today's boat buyers generally don't have a clue about the systems on a boat and are not interested anyway. So if they see something dripping or some water in the bilge, they panic and think they're sinking. The dripless seals, he said, were simply a gimmick to provide peace of mind.* This from a guy who sells them.......


-- Edited by Marin on Friday 15th of January 2010 10:40:57 PM
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Old 01-16-2010, 12:12 PM   #15
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RE: stuffing box replacment

Hah, now Im in Lima hoping I can get the NFL playoffs. Marin, my ER is walk in and it is great fun to IR gun the 6-8 temp spots per engine*and check things out. Plus Im a gear head. So all the remote sensors in the world could not keep me out during cruising. That is why I buy boats rather than race horses

Two* questions

Marin:
If you won the lotto and bought a new(er) GB or Aleutian, virtually all of which have dripless, what would be your go forward actions regarding the dripless units you purchased.

rickB:
What is the minimum shaft size that could accomodate a safety bladder arrangement and are they used on the smaller shafts that you know of.
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Old 01-16-2010, 12:43 PM   #16
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RE: stuffing box replacment

Quote:
sunchaser wrote:

If you won the lotto and bought a new(er) GB or Aleutian, virtually all of which have dripless, what would be your go forward actions regarding the dripless units you purchased.
Good question.* I certainly wouldn't replace them unless I was told that dripless seals are really trouble-prone and a failure waiting to happen, in which case I might think about replacing them with standard packing.* But I've not heard that they are and I doubt that GB, Nordhavn, etc. would use them if they were.* So I would simply check them routinely along with everything else in the engine room.* Right now on our boat, that is once during a day's cruise, usually an hour or so after departure when everything is up to temperature.* I also check the engine room before we start up and after we shut down.

However..... if I learned that dripless seals really do require checking every hour--- which is what you say you do--- I would definitely change them for something else because no way in hell am I interested in* crawling around in, or walking around in, a stupid engine room every hour.* The fact that you do this says to me that you have some inherent mistrust of the seals, which in turn tells me maybe they're not all that reliable as they're made out to be.* So if an hourly check is the kind of scrutiny they require to maintain confidence in them, at that point this becomes cause in my mind to get rid of them.* I love operating engines---- I've said before I wish our boat had three of them instead of just two--- but I have absolutely no interest in hanging around watching them or any other system on the boat.* There are more interesting things--- at least when boating in this area-- to watch.

But if dripless seals are truly reliable, or as reliable as anything can be on a boat, it wouldn't bother me at all if our boat boat had them.

Standard packing glands have a track record of a couple of centuries of reliable, no-worry service.* I'm not a big fan of using technology simply for technology's sake, which is one reason I work for Boeing and not Airbus. My point is not that dripless seals are dangerous so they should be changed if a boat has them, but that if a boat doesn't have them there is no bang for the buck in installing them.
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Old 01-16-2010, 02:22 PM   #17
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RE: stuffing box replacment

Quote:
sunchaser wrote:

What is the minimum shaft size that could accomodate a safety bladder arrangement and are they used on the smaller shafts that you know of.

*
Am not sure but have seen them on under 4" diameter (550 hp vp on a sailboat). The Manecraft seals I mentioned earlier fit shafts down to about an inch. They don't use an inflatable bladder but have a built in section that rides close to the shaft and can be compressed around it with a hose clamp sort of attachment.

If I were to order a newbuild that came stock with dripless seals of the type we have been discussing rather than a stuffing box, I would specify a change to either a stuffing box, the Manecraft style, or if it was a larger boat, the type with an inflatable bladder.

There simply is no justification for installing any device with moving parts that, when it fails, will lead to rapid and uncontrolled flooding and loss of propulsion.
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Old 01-20-2010, 08:53 PM   #18
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RE: stuffing box replacment

You need about 12 inches of shaft to work with for a PSS system, less with a TIDES.* The reason for dripless shaft seals is because they are, well, dripless.* If that matters to you and you can easily see the shaft seal then I wouldn't worry that much about the technology.* The rubber used on the PSS bellows is quite thick, and as long as you inspect it every once in a while for cracks, I'm not sure what the panic is.* Packing glands are tried and true and as long as a little wet in the bilge doesn't bother you, why change, but if it does the dripless systems work well, IMHO.
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Old 01-21-2010, 03:28 AM   #19
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RE: stuffing box replacment

I seem to recall the reason given for the loss of a florida bay coaster was something* coming loose in the er and tearing the bellows on the dripless shaft seal.
*True things shouldnt be flying around in ruff weather but murphy does crew on every boat .
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Old 01-21-2010, 10:19 AM   #20
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RE: stuffing box replacment

Quote:
Delfin wrote:

*I'm not sure what the panic is.*


*
I don't think anyone is having a panic attack. It has been a rather mild discussion about a piece of what I would call "elective" equipment and its virtues and faults.

Like I said, I wouldn't choose to replace a bulletproof piece of equipment with something that has a failure mode that is all but certain to lose the vessel, nor would I install one.

*
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