Idiot Question - Dripless Shaft not so dripless

[Johnathon123]

I am not very familiar with shaft engines (had a saildrive forever until now) so take it easy.

My new to me boat appears to have a fairly high rate of water ingress (about 2 buckets a day - I am managing that).

I excluded my usual causes and turned to the shaft.

The shaft appears to be fitted with a PSS dripless according to the instruction manual in the pile of papers.

My thought is that whoever installed this thing has done a dreadful job but I may be wrong.

The photo (really sorry about the quality quite hard to get too) shows the stuffing box (the green nut at the back) adjacent to the the thru hull for the shaft and then you can see the PSS seal. All of my reading suggests it needs to be the other way around and the PSS should be wrapped around the shaft thru hull.

So if I am right, and that is a big if, how does one fix this? Can it be done in water? is there a temporary fix I can do? etc

Any advice is always greatly appreciated.

https://goo.gl/photos/EsoHyqrgwiSFbNFq8

[Emmalina]

I would say that whoever installed the pss seal left the possibility to re-use the stuffing box if need be. Only problem with that is there will be very little play in the shaft. Depends on the coupling to the gearbox. Apart from that they recommend changing the gator every 5 years. Just done mine.

[Snowpetrel]

Looks a bit nasty! I can only see one photo in the link, and nothing on your post, but it seems to be leaking where the old stuffing box attaches to the hull/shaft log/stern tube? If this is the case it might be a tricky one to fix. And the risk is that the whole part might come loose making for a much bigger leak.

Maybe wrapping the whole lot in rescue tape might slow the leak if its on part of the tube.

It might be possible to get a diver to seal the shaft where it exits the hull so you can work on it in the water. But much better to do this kind of job on the hard where you can pull the shaft and take your time.

Sent from my SM-G930F using Cruisers Sailing Forum mobile app

[Alan Mighty]

James: Hi!

It does look like a PYI PSS seal.


An unusual installation - it seems that your boat only has a tiny length of shaft exposed between the stern tube (aka shaft log) and whatever the white metalwork at lower right of your picture.


What is the white painted metal at lower right of your pic: a transmission/gearbox?


The leaking all seems to be at the aft end, suggested by the stains on what I guess is the inside of your transom and the green colouring of what I guess is bronze.


I think your next step is to identify the source of the leak:


1. through the transom, perhaps via a crack or other fault; or


2. through the stern tube; or


3. at the point where the PSS bellows is clamped to the stern tube.


I read your post as you suspecting that the leak is at #3. That's possible, but your photo doesn't rule out #1 or #2.


I do note that the PSS bellows is secured by hose clamps:


* two at the forward end (where the bellows is clamped to the PSS rotor); and


* one at the aft end (where the bellow is clamped to the stern tube - there may be a second hose clamp, but I can only see one). I cannot see the tensioning screw on that aft hose clamp.


I personally don't like common stainless steel hose clamps of that screw-and-band style (the so-called Jubilee clip) unless they are doubled. And even then, I'm not keen on them. I prefer T-bolt clamps (e.g. https://www.whitworths.com.au/main_i...asp?item=44215).


My first suggestion for your consideration (other folk will be along soon with completely different ideas) is to check and adjust that aft hose clamp on the PSS bellows. I'd suggest:


* first equipping yourself with a T-bolt clamp that would suit that diameter (it is likely the same diameter as the forward hose clamps; calipers would measure that for you).


* second, with a T-bolt clamp as a spare/replacement, then do your best to check and adjust the tension in that aft hose clamp. For all we know, that hose clamp may never have been tensioned properly. Or it may have already broken (typically, seawater plus mechanical stress leads to corrosion of the metal band of the hose clamp right beside one of the slots cut for the tensioning screw to bite on). And that's the reason I think you should have a spare/replacement when you check that hose clamp - it might already need to be replaced or it might break when you try to tension it further.


As long as you have a healthy bilge pump, you can do that with the boat in the water.


If you measure the hexagon of that most accessible tensioning screw on the second forward hose clamp, you can choose a socket wrench of the same size. And try to put that socket wrench on the head of the tensioning screw of the aft hose clamp - it looks like you're going to need to do that blind, i.e. without being able to see the tensioning screw.


I'm concerned by that staining on the inside of your transom. It may be water that has run aft from the PSS. Or it may be water leaking through the stern tube or through the transom.


The transom is timber, right? You've checked the soundness of the timber with a probe? That would rule out rot.


If you can rule out leaking through the transom and leaking from the PSS bellow/stern tube connection, then I would suggest you focus on the likelihood that the stern tube might be leaking.


Note that you can see a video of recommended installation procedure for a PSS at: PSS Shaft Seal

[Alan Mighty]

Steve's comment (Emmalina, #2) makes me think that the Previous Owner had a problem with the old stuffing box. And thought that adding a PSS might solve the problem.

And if that's the case, it points very much to the problem being with the stern tube or old stuffing box.

[Johnathon123]

Thanks everyone. I really appreciate the advice. Sorry about the photos.

Here is a second one. https://goo.gl/photos/bvTpS5NRpXaVTAGd7

The boat is old, but the shaft, engine and propellor were all replaced 18 months ago which is why this baffles me.

The rear is the transom, solid as oak with a probe and no evidence of any other damage when cleaned up. Access is poor, I have just got my hands on a camera on a wand from a mechanic mate so hopefully better ones soon.

The bellows do not appear to be connected to the stern tube at all to me as the stuffing box is between the bellows and the stern tube?? Am I just super ignorant.

I will go ahead and check the hose clamps and set about replacing them.

How tight are they supposed to be? Super tight?

If the stern tube is leaking, slip right??????

Thanks again, much appreciated.

BTW: The white bar in the right corner is a rib and is about 15cm below the shaft or thereabouts.

[Alan Mighty]

Originally Posted by Johnathon123

Here is a second one.

Showing that a second hose clamp is deployed on the aft end of the PSS bellows.

Also showing that all the leaking is aft of the PSS bellows and that the PO's installation of the PSS bellows is to specification.

The bellows do not appear to be connected to the stern tube at all to me as the stuffing box is between the bellows and the stern tube?? Am I just super ignorant.

You're no more ignorant than the rest of us, James. We all learn from mistakes (preferably those of others, not our own). No one gets born with the knowledge, skills, and ability to maintain a boat.


The PO had done the job without removing the stuffing box for some reason unknown to us.

And by doing so introduced the risk that the leak might be at the junction between the stern tube and the leftover bits of the stuffing box.

I will go ahead and check the hose clamps and set about replacing them.

How tight are they supposed to be? Super tight?

No need to go overboard with replacing the hose clamps. Check them. I'd suggest making your next purchase T-bolt clamps instead of hose clamps. T-bolt clamps are more expensive. But for fitting below the waterline, T-bolt clamps are worth it.


Hose clamps and T-bolt clamps can be overtightened.


If using a screwdriver to torque them, you would need the arms of a gorilla to overtighten. If using a socket wrench (I like a small 1/4" drive socket wrench - the ratchet action means you can use them in confined spaces; and an extension bar can also be useful), you could overtorque a hose clamp.


When screw-and-band hose clamps are overtightened, that stress in the presence of chloride ions from seawater leads quickly to stress crack corrosion. So the edge of the band, next to one of the slots acting as screw thread, cracks. Sometimes with a tiny fuzz of corrosion around the crack.


Note that SCC breaks screw-and-band hose clamps that are not overtightened too!


The rule of thumb (especially with fuel hose or other thick walled hose) is to not distort the hose. When using a screw-and-band hose clamp, if the torque causes rubber to extrude through the slots in the band, then the clamp is over-tight. If the clamp is so tight that its diameter is significantly thinner than the diameter of the un-clamped portion of hose, the clamp is likely overtight.


Figures such as 2.5 - 3.3 poundforce.foot (lbf.ft) or 0.3 - 0.46 kgforce.metre (kgf.m) are usually in the right area. Depends on the size of the hose clamp. Manufacturers of quality hose clamps will quote the max torque figure (but by the time hose clamps get to a supply bin at your local chandlery, those figures are no longer around).


See for example: Hose Clamps Part II: Installation and Use | Steve D'Antonio Marine Consulting

If the stern tube is leaking, slip right?

Yes. That would give you opportunity to check the stern tube and work out a better way (if possible) of securing the PSS bellows directly to the stern tube if possible. Check the cutless bearing for play too.

[Johnathon123]

Thanks Alan.

I really appreciate the advice.

I will let you know how we get on.

James

[Emmalina]

I generally tighten things till they stop leaking ! Its easy to chop rubber with an over zealous screwdriver !

[lesterbutch]

Don't make the mistake of doing this wet! You must put yourself in a position to be able to carefully examine all parts and even more carefully replace them! You can't do that when your fighting water flowing in. Plus you want to examine both ends of the job! You can always take the opportunity to re-paint the bottom��

[davewtsnape]

I don't see how you can have stuffing box and PSS. The PSS should not leak at all! Something is seriously screwy. The bellows should be secured to the stern tube at the aft end and the stainless collar at the other.

[JOHNMARDALL]

I can't open your photo but from your description it sounds as though the PSS bellows hose has been installed over the old stuffing box which should have been removed so that the hose could be clamped onto the shaft log (tube). When you disassemble it (out of the water) you may find that they've clamped the hose to the hex nut of the old stuffing box. PYI are in Washington State and offer excellent parts service and advice
Good luck
John Mardall
Vetus Group

[Johnathon123]

Thanks again everyone. Info much appreciated.

Further inspection suggests that the leak is coming from the old stuffing box. (no better photos I am afraid).

So in my simplistic mind I see a problem. There is very little room between the old stuffing box and the PSS Seal. Backing it off and replacing the flux is not really an option.

I suspect, given the former looseness of the hose clamps that the PSS Seal (aft) used to wrap around the old stuffing box or even the stern tube itself.

So my new and improved question is

Can I back off the hose clamps, let a little water in, cover the stuffing box with the bellows and then reconnect the aft edge of the bellows to the stern tube?????

Please go easy on me, as I write this I am a little scared by how little I know.

As always, thanks in advance for any comments.

[JOHNMARDALL]

Hello again,


I realize that you don't want to take the boat out of the water, but suspect that you also don't want to sink her. The PYI PSS dripless seal is not designed to go over the old stuffing box. To do this right, you have to remove the stuffing box and attach the bellows hose of the PSS seal directly to the shaft log (tube). The bellows hose may already be damaged by having been clamped on to the old stuffing box and if so, will need to be replaced, but you just can't do half on this - you will sink your boat and maybe its captain and crew.


Sorry mate,
John Mardall
Vetus Group

[Johnathon123]

Thanks John, I tend to agree, but sometimes I like to test the simple ideas before tackling the big ones.

Thanks again. She will be on the slip soon.