Shaft Seals

from the

Sailnet Tayana List

I want to replace the stuffing box with a PSS dripless seal but I can't get to the stern tube to take the measurements. According to one of the mechanics in my yard, to install a PSS you have to pull off the stuffing box, reverse it (so it's flange to flange) and reinstall it so that you have some stern tube projecting from the housing. I don't know that I fully understand all that but I do understand that I will have to pull the boat to get the measurement I need to order the part.

Anyone have the dimensions handy? April 2000

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Subject: Dripless Shaft Seal

I think all you need is the shaft diameter, probably 1 1/4" and the tube OD 1 13/16". That means you probably want to order the next size smaller hose, 1 3/4". They'll stretch. Of course that's assuming you have a Tayana 37 with the same packing gland as my 1978 hull 123. Nothing against PYI, they are excellent but have you considered the Tides Marine Strong Seal?

Ray Slaninka, Tayana 37 April 2000

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Ray,
I see 2 problems with the Strong seal:

1) They're rated for 2 years/2500 hours. Forgive me for saying it, but that's not much--especially when you consider the repercussions of failure.

2) They require pressurized water (or at least the web page implies that fact)--the PYI seals don't need that, at least not at slow sailboat shaft speeds.

I like the PSS because:

1) the stainless/carbon seal lasts for ages--not as noncorrosive as pure plastic, I suppose, but my shaft is already stainless

2) No need to use water cooling

Strong is a great company, though, and I look forward to the arrival of my new mast track.

Erik April 2000

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Subject: Dripless Shaft Seal

Hi Eric:

As far as the Strong Seal goes you hit the nail on the head as far as what turned me off about them at first. But I wonder if the same low rpm theory applies to the longevity of the Strong Seal as well. I think the 2500 hours is at high rpm. Other factors in favor of the Strong Seal are "supposedly":

1. You can buy a spare seal, which mounts on the shaft at the time of the original install, so if the seal needs replacement, you have the spare ready to go already on the shaft.

2. It is a lip seal so if it does leak it is not catastrophic. The PSS can let a lot of water in if the seals separate. I used to have a Lasdrop, same type seal (PSS is better I think), same potential for misalignment type leaks. However it served me well as long as the engine did not move too much on the rubber mounts. When that happens they leak.

3. A pressurized water supply eliminates the possibility of air getting trapped in the stern tube causing the seal to overheat. At high rpm even PSS requires a pressurized water supply. However it does cause an installation problem. Plus lip seals are relatively new.

4. It is self-aligning, meaning the seal is on the shaft and moves with it.

5. You do not have to ever burp the seal to make sure no air is in it. There may be a work around for this on the PSS. They sell a hose barb for the pressure water option. It is possible to use the hose barb as a vent by running a hose well above the water line so air can escape.

After all is said and done, I have had a hard time deciding. I think I would sleep well with either but with the Lasdrop I did have to get used to relying on the stern tube hose/bellows to keep the seals in contact with each other. By the way, that hose also has a life expectancy and may lose it ability to mate the two surfaces of the seal.

So, for this season I am going to just try the dripless Teflon packing. It is easily repaired with conventional flax that can be obtained anywhere in the world and repaired while at sea and does not necessitate carrying expensive spares as for the dripless type seals.

Basically I talked myself out of using one for now!

Ray Slaninka May 2000

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Harvey:
Perhaps you missed these threads. I think both units are good, never heard of any problems with either unit from anyone, but I lean toward the Strong Seal, especially with the extra seal pre installed for replacement as long as you don't mind plumbing it to the cooling system.

Also, here's the URL:

http://www.tidesmarine.com

Ray Slaninka May 2000

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Phil
Can't help with any suggestions re removing the stuffing box in the water.

I have a PYI dripless gland installed - works fine and to my thinking the design is sound. If you go to the web site www.pyiinc.com there is a section on installation, looks pretty straight forward.

The PYI had been installed by a previous owner complete with new prop shaft. The old shaft (still on board) was badly worn - concaved around the packing gland area. Maybe this has happened to yours ??

Bill Moloney Covenant lll October 2001

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Subject: Pulling shaft

I think people are missing the point of the question. He is asking about the pillow block bearing the shaft runs through about 18" in front of the stuffing box. Gear pullers (unless you find one with ears 4 feet long) won't work.

I haven't had to remove mine yet (am going to this fall), but what has worked for me in similar situations was to carefully heat the hub of the bearing (without heating the shaft itself up too much), then let it cool. Heat it again, then use a hammer to knock the bearing off the shaft. You can also use ice to cool the shaft while you heat the hub. Be careful not to hit the shaft with the hammer, though. If you use a soft (brass) hammer, you will be less likely to damage the shaft.

After you get the bearing off in this manner, it is a good idea to replace it. Heat and banging tend to damage the race and balls, and they will often fail soon after reinstallation.

Frank Timmons V42 Magic Dragon Deltaville, VA August 2003

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I was able to fit a socket of slightly smaller dimension than the shaft between the hub and the tranny and bolted it back together using longer bolts, After "pressing" the shaft out a bit, I switched to a deepwell socket and repeated the procedure. All in all, it went rather smoothly.

Tim Pruss S/V Chardonnay Tayana Mariner36 August 2003

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Just a quick update of my stern tube and cutlass bearing replacement project in case someone is contemplating doing it, too.

After breaking three of the four studs which secure the stern tube assembly to the deadwood and then removing all parts of the broken studs from the deadwood area I found that Tayana screwed the studs into deeply (two inches) embedded hex nuts located in the deadwood. All four hex nuts had short pieces of metal rod welded on each side of the nuts as anchors. They were the same deal I found when I replaced all my chain plate studs.

I removed each of nuts and filled the holes with thickened epoxy, a little at a time, until they were full. I am going to drill and tap the epoxy to accept bronze hex cap screws (1/2" x 3") in lieu of the studs. Hopefully, I'll be able to replace the cutlass bearings much easier in the future.

Regards, John Keefe CT37 ODYSSEA Youngstown, New York August 2003

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The zinc collar on your boat's propshaft probably has minimal effect on water circulation within the cutlass bearing since water from your engine's seawater cooling system is injected directly into the PSS shaft seal/tube/cutlass bearing (in addition to what comes in through the lateral slots in the bearing). On boats with traditional stuffing boxes and no water injection, however, an anode placed too close to the cutlass bearing can restrict water circulation and the stuffing box will become warm to the touch.

You get lots of water when burping the PSS shaft seal due to the pressure differential inside/outside the boat. However, that pressure differential doesn't affect water circulation within the seal/ tube/ bearing once the seal is reseated. That's why PYI provides the hose barb on the PSS seal - so that water can be injected to keep the seal/tube/bearing cool.

Fortunately, you don't have to have a zinc collar on the prop shaft, you can bond the shaft with a shaft brush mounted inside the boat. Since it doesn't have to be replaced annually like most zincs, a shaft brush will actually save you money.

Sue Canfield March 2004

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I'm curious about this. Kamaloha has had a zinc in that spot for as long as I've owned the boat; I just repeated what the previous owner had done. As you point out there is very little space between the zinc and the end of the cutlass - about 1/8". However, the aft cutlass fitting has slots in the sides with what look like little vanes to direct water flow coming aft into the bearing. I know that when I "burp" the PSS Shaft seal on the inside I get a prodigious water flow, so I don't think the zinc is blocking enough to hurt anything. The last time I pulled my prop shaft for inspection it and the cutlass appeared to be fine.

Charlie March 2004