stuffing box question

[peb]

Probably a dumb question, but here goes.

Ok, my boat has a PYI dripless shaft seal. I have never had any trouble and regularly check it, in particular making sure the set screws do not work loose. However, after reading one too many horror stories and since I just hauled the boat to the shop for maintenance, I am considering replacing it with a stuffing box. Now, I know nothing about stuffing boxes. I have found a couple on the web to purchase, but would like to know what I am getting myself into. The shaft goes through a 1 inch fiberglass tube which extends inside and which the current dripless seal is attached to. What am I in for on the replacement? Does the stuffing box mount directly on the same tube? What maintenance is involved? What makes a stuffing box so much more secure? Of course I can see how the dripless shaft seal could fail, but how do stufing boxes not have any catastrophic failures?

[Dan McCosh]

Short answer is that they do--mainly loss of lubrication, seizing up, or something similar. It's also possible to spin the nut off one.

[Gary E]

You have a good if not the BEST ...why switch back to horse and buggy days???

Any of these names familiar to you???

http://www.google.com/search?hl=en&q=PYI+dripless+shaft+seal&btnG=Google+Search

http://www.shaftseal.com/manufacturers-who-use-pss-shaft-seal-as-standard-equipment.html


Boat Builders Fitting P.S.S. Shaft Seal
As Standard EquipmentAlden YachtsAzimutBaha Cruisers ( F.R.P.)
Bayliner (U.S. Marine)
Blackwatch (Little Harbor)
Donzi Yachts
Duffy & Duffy (Atlantic Boat Co.)
DuskyFormula (Thunderbird Products)
FreedomHunter MarineIsland Gypsy (Halvorsen Marine)Kvichak MarineLegacy MarineLittle HarborM.B. SportsMaxum (U.S. Marine)MerrittMorgan YachtsNordic TugsNorthern MarineOcean Alexander (Alexander Marine)Ocean YachtsQueencraft (Marine Transport Service)RoscioliRybovich-SpencerSabre CorporationSilverton Marine CorporationSwan (Nautors)Tiara (S-2)WellcraftWhiticar Boat Works



http://www.shaftseal.com/pictures/1pblacklinehorz.gif
PSS Shaft Seal




12532 Beverly Park Rd.



Lynnwood, WA 98087-1524


http://www.shaftseal.com/pictures/bottom-pss-shaft-seal.gifToll Free: 800-523-7558
Fax: 425-355-3661
Email: Info@ShaftSeal.com (info@shaftseal.com)

[willmarsh3]

I have a stuffing box on my steel ketch. I've had the boat for 10 years and have not had to mess with it except for occasional tightening of the nut.

Good overview of stuffing boxes here:
http://www.alohaowners.com/pages/projects/stuffing/stuffing_box.htm

[chergui]

I wouldn't change it if you don't have a good reason to. The stuffing box is larger than the diameter of the shaft, which goes through it. Inside the stuffing box are 3 or 4 coils of packing that are wrapped around the shaft. Each coil is snug around the shaft and the top of the stuffing box making a sort of seal that prevents water from coming in the boat. There is a nut that compresses the packing. Over time the packing will wear and you'll tighten the jam nut to prevent too much water from coming in. When the engine is running, you have it tightened so that water drips about once every 20 seconds and it doesn't drip at all when the engine isn't running. The dripping is what cools the shaft. If it's too tight you can burn the packing. It will also be running too hot and you may score the shaft. The packing wears gradually so it won't suddenly fail on you. But you frequently have to check the drips. You also have to pump the bilge. I think there a dripless system is quite nice personally, but if I were offshore I might reconsider.

I think the lifespan of the packing varies depending on how well you maintain it. Mine didn't have enough rings and I probably didn't pay quite enough attention to it. It lasted only 3 years. To repack it you unscrew the jam nut and slide the stuffing box up the shaft, pull out the old packing and put new packing in.

You should also consider that the prop is spinning the shaft when you're sailing and this will wear the packing. A shaft lock is helpful.

If you're happy with the dripless system though I don't think it's worth the effort to change it. Many people use them and they don't fail regularly.

[ssor]

I have been running a dripless PSS shaft seal for 8 years. The set screws are doubled up . That is the first is installed and tightened and a second is installed on top and tightened. There is a dimple in the shaft for the set screw to seat in and there is a mark on the shaft for position. There are some concerns about overheating the seal but "burping it at launch is all it needs and the newer models even have eliminated that need. I understand that the bellows is kevlar reinforced and I haven't heard of any failures of that component.

[donald branscom]

You ARE making the right decision to use a regular stuffing box.
FORGET that "horse and buggy days" stuff. By the way old cars had grease fittings to lube the water pump bearing. Now they have done away with that and replaced that with a "sealed" bearing, (actually just dipped in plastic or rubber sealed bearing.) Trouble is when the bearing starts to get hot corrosive anti freeze in it, all lubrication is lost and you are in for an expensive repair. But the SAE (Society of Automotive Engineers say that putting ONE tablespoon of brake fluid in the radiator (basically hydraulic oil), the oil will disperse into the coolant and lube the bearing. I have extended the life of a water pump for up to 6 months with this method. The squeeking stopped instantly. So that "Horse and Buggy days stuff is not always the best advice.

Now back to your stuffing box. The stuffing box will attach with a short rubber hose to your fiberglass tube. The stuffing box is usually sold with the rubber hose and clamps.

Do not over tighten the nut. If the bronze feels hot, then the nut is obviously too tight..
But the best insurance is to install a grease fitting into the fiberglass tube and install a grease fitting and fill the prop shaft tube with polypropolene grease. It will not leak a drop.
I am telling this to you from ACTUAL EXPERIENCE.

The reason a stuffing box IS BETTER is that it is low tech and almost anywhere in the world you can find parts or repair it. The fancy high tech carbonseals of the SO-Called dripless seal can be harder to repair and get parts for.

The regular marine stuffing box can use different materials for the seal and different materials ARE available to use for the seal.

When you go into West Marine I do not think you will find parts for your high tech seal. Right? Also the regular stuffing box does not require disconnecting of the engine or shaft to replace a seal. THINK ABOUT THAT.

[Pierce Nichols]

The reason a stuffing box IS BETTER is that it is low tech and almost anywhere in the world you can find parts or repair it. The fancy high tech carbonseals of the SO-Called dripless seal can be harder to repair and get parts for.


Well, that's a function of what he's planning to do with his boat. If he's going cruising to all sorts of interesting and remote places, then it's a concern. If, OTOH, all his cruising grounds are places where FedEx/DHL/UPS deliver to regularly, then getting the parts is less of a concern. A full set of spares onboard and the skills to fix the seal are an excellent idea regardless.



Also the regular stuffing box does not require disconnecting of the engine or shaft to replace a seal. THINK ABOUT THAT.

Now that's probably the best argument I've heard for an old-fashioned stuffing box. :)

[Lew Barrett]

I would stay with the girl you brought to the dance. I have had no issues with my dripless equipment; love it in fact. Look and check once in a while and you'll be fine. Why go through all the effort to go back to the dripper? It makes no sense. What you have, as has been said, is top of the line. If you are concerned about replacement seals, wrap one upstream of the system on the shaft. If you have a failure, just pull the old one out, cut it off and push the new one in place. That's what we did. Should be good for twenty years. Or more. Couldn't be easier, could it.

[peb]

Thanks for the advice all. Perhaps I am just paranoid.

[donald branscom]

A stuffing box is supposed to drip one drop per hour.
When you fill the prop tube with grease there is NO DRIPPING at all.

[Bob Cleek]

Ditto to Don's advice. What I have done, although not an original idea, is to run 1/4" copper tubing from the grease hole fitting on the box up to a convenient spot in a cockpit locker and attached a grease cup on it. In that way, whenever I feel the urge, I can give the grease cup a twist until it is firm and know I've pumped the tube full of grease. Adding more grease is simply a matter of screwing off the grease cup and refilling it. With the copper tube extension, there's no hanging upside down in the bilge to reach the stuffing box. Consequently, this routine maintenance task is effortless and thus done when it needs to be done.

[willmarsh3]

Does the grease go in where the packing is? Or does it go down in the prop shaft tube out to the cutlass bearing?

The reason I ask is on my steel ketch there is a small hole in the propeller shaft tube just forward of the cutlass bearing that allows water to circulate past the cutlass bearing and cool it. When I bought the boat the cutlass bearing had become fused and no good evidently because said small hole had become fouled and clogged. I got it fixed before even putting the boat in the water.

I would think that grease being squeezed down inside the prop shaft tube would eventually reach this hole and/or the cutlass bearing and interfere with the water circulation.