Standard stuffing box vs. PSS seals vs. "self aligning" gland

[Breakin Away]

I am continuing to diagnose and map out a plan to fix the problem described here in another thread. I am seeing bronze flecks dripping from my standard stuffing box:

I think I am going to do some additional inspection and measurements before buying anything. When placed into gear, the torque of the motor pushes the shaft up (slightly) and to port (mostly), causing shaft-to-nut contact
at about 2 o'clock when looking aft toward the nut...

A few additional facts:

I originally discovered this issue when I put a white tissue under the stuffing box to help detect dripping water, and found fine bronze particles. At that time I did not know how long the problem had been happening. I've been putting down the tissues periodically for awhile, but this time I happened to have some sunlight hit the tissue at just the right angle to see some shiny specs, which led me to get out a magnifying glass and take a closer look.

Alignment appears to be fine when the motor is in neutral or not running. The packing nut is well centered on the shaft in this state, with an even 0.01" gap. The issue only appears when in forward, and gets worse at higher RPM (due to higher torque on the mounts).

The stuffing box was replaced in early 2019, along with original bronze shaft (Aquamet G22 upgrade), strut, prop, and coupler. I just inspected the old stuffing box and shaft that were removed at the time, and can clearly see wear patterns that suggest that this issue had been present (and undetected) for quite awhile before 2019. I purchased the boat in 2016, and not sure the surveyor would have detected this.

There are no vibrations in the system, except for idling below 900 RPM (according to the console tach). I have it on my list to recheck the idle RPMs using a strobe on the motor - it might actually be below the M35B spec of 800-1000 (Service Bulletin #236). Getting up to 950-1000 immediately eliminates the vibration. The <900 RPM vibration happens in neutral, so it appears to be unrelated to running gear or alignment...

The first mechanic who looked it over suggested that I need new motor mounts. I am not convinced that this would actually solve the problem, and since the mounts are very expensive I'm looking for a second opinion before getting into a high-dollar replacement. I spoke to another mechanic this week who suggested switching to a "self-aligning" gland. I've searched around to try to see what he's talking about, and the closest thing I found was this:

https://www.go2marine.com/Bronze-Packing-Boxes-Self-Aligning-Gland-Type

So far as I can tell, these are not available for 1" shafts, and the guy said that what he has in mind actually requires tapping into the cooling system. I asked if he was talking about a PSS seal, and he said no, this is something different. So I'm not sure exactly what he is suggesting.

But that got me to thinking, why not just do a PSS seal?

I'd be interested to hear your comments about the various options that you may have used instead of the "standard" packing box? Does anyone have a PSS seal? Other type of packing box?

[Noah]

Countless users out there. There are over 100 references/posts regarding PSS dripless seals on this website. Why not just search and read?

[Breakin Away]

Countless users out there. There are over 100 references/posts regarding PSS dripless seals on this website. Why not just search and read?

I've started reading them. However, PSS changed the design recently, so there may be new comments relevant to the more recent version.

I'm also interested in the "self aligning" one, and haven't found anything about that in my searches, so I thought it would be good to have a thread that compares all the options.

[Patches]

Did all the back and forth myself last December when I put in a new SS prop shaft.

Initially, I thought I would put a new stuffing box on and continue to do it the old "tried and true" way.  Even bought a new stuffing box.  Even went down a dark and long rabbit hole about whether or not to use the new graphite impregnated flax material, including considering the cautions from Mainesail and others about it possibly leading to corrosion on the (new) prop shaft.

Got down into the aft cabin and started working on it, and changed my mind.  Returned the stuffing box, bought a PSS, and installed it.  Love the simplicity, and no issues.  New PSS units come with the nipple to remove possible ventilation when backing (thereby potentially removing water from the PSS bellows which might cause it to overheat). Attached a piece of hose to the nipple with a hose clamp, and ran it up above the waterline to an overflow/ventilation doohickey as recommended by Mainesail.  Located mine just aft and below the sink in the head inside the sink cabinet.

Again, no issues since and as a charter boat I'm out 3X/day, 6 days/week, May-September.  I highly recommend changing to the PSS. 

Patches

[Noah]

Okay... but why? What were your issues with a "traditional" stuffing box? I have a traditional stuffing box, with GTU packing. It keeps my SS A22 shaft cool and barely drips, even when running at full speed—after 5 years. I pulled the A22 shaft in 2018, as I was replacing my strut (documented here on the forum), and the machine shop said it was true and like new—no evidence of heating or scoring. IMO, the dripless seal adds a potential catastrophic failure point. Let the opinions fly...

[Breakin Away]

Okay... but why? What were your issues with a "traditional" stuffing box? I have a traditional stuffing box, with GTU packing. It keeps my SS A22 shaft cool and barely drips, even when running at full speed—after 5 years. I pulled the A22 shaft in 2018, as I was replacing my strut (documented here on the forum), and the machine shop said it was true and like new—no evidence of heating or scoring. IMO, the dripless seal adds a potential catastrophic failure point. Let the opinions fly...

The mechanic thinks (pending further evaluation) that my engine and shaft are aligned properly, but that the stuffing box and hose are not aligned properly with the shaft, thus leading to the bronze flakes due to stuffing box contact with the shaft. He is suggesting something that will better center itself with the shaft. This could be the PSS, which there is no shortage of information on, or some other type of bronze self-aligning stuffing box, which is different in some way from the current standard stuffing box, but which I have yet to be able to get any information on.

People have told me that there are "horror stories" about PSS, but I have not found any specifics.

I agree that the old fashioned stuffing box works great -- until it doesn't, which is the situation that I am in now.

[Noah]

Break'in—I don't get it?!? I am not a mechanic, but simple geometry should rule here... if your engine coupler, shaft, stern tube and strut are all aligned at the correct height and angle relationship, it should NOT matter what your stuffing box is (i.e. traditional or dripless). I don't think changing your stuffing box will solve whatever "problem" you are having.

[Breakin Away]

Break'in—I don't get it?!? I am not a mechanic, but simple geometry should rule here... if your engine coupler, shaft, stern tube and strut are all aligned at the correct height and angle relationship, it should NOT matter what your stuffing box is (i.e. traditional or dripless). I don't think changing your stuffing box will solve whatever "problem" you are having.

As it was explained to me, everything can look great when you line everything up without the motor running. But when the motor starts spinning the shaft, things can shift. The motor can move to port due to the prop/shaft's torque resistance on the engine, small vibrations on the engine can transmit through the running gear, etc. It doesn't take much movement, because the stuffing box is only 1.02" ID (with a 1.00" shaft). So a movement of 0.01" can lead to metal-to-metal contact.

The standard shaft hose is very thick and stiff, so it will not "give" much. The PSS bellows flexes much more, so that could help things. I'm told that the gimbaled self-aligning shaft will also flex a bit, though I haven't seen its design to see exactly how it does this.

My standard stuffing box seemed to be working fine for 6 years, but suddenly started shedding bronze flakes. It was replaced 2 years ago. I looked at the old one that was taken out, and it looks like that one was showing signs of metal-to-metal contact too. Maybe I just didn't notice it.

I am searching for the solution to this problem. One hypothesis that I have is that my Teflon packing is too soft and wore unevenly over the past two years, so there was no metal-to-metal contact until it wore down 0.01" on one side.

Another possibility is that the engine mounts are worn and allowing more movement of the engine than before. But still, it only takes 0.01" of movement to cause this problem, so I could spend $1200 on new engine mounts and still have the same problem. That's why I'm searching for the answer, since I think $1200 is a lot to spend for something that may not ultimately fix my problem.

[Noah]

Gave you my two cents...anymore, can't help ya...good luck on your quest.

[Breakin Away]

Gave you my two cents...anymore, can't help ya...good luck on your quest.

Your help is appreciated. I've tried adjusting my current setup for the past 6 weeks. I've "clocked" the stuffing box, loosened/re-tightened the shaft hose hoping it would align itself, tightened the nut, loosened the nut, etc. It looks perfectly aligned when the motor's not running, but when I put it in gear, bronze flakes appear.

Now, with winter haulout, I have an opportunity to do something more major, since the minor DIY stuff isn't working. Two mechanics have told me two different things, so I don't know which to follow. All I know is that next spring if it isn't fixed I'll have agony all spring/summer, and then would probably need a midseason haulout to try something else.

[Patches]

For Noah:

"No issues" means no leaks, no chance of scoring the new shaft, and no repacking of flax.  Glad to hear there are no adverse affects of the graphite impregnated flax on your new shaft!  Wasn't sure how to weight that criticism of the GTU.

Interested though in the "potential catastrophic failure point."  A traditional stuffing box relies on a hose connection between the shaft log and the packing gland, attached with some hose clamps.  A PSS relies on a bellows instead of the hose, which is in compression, but is still a kind of hose.  A SS rotor affixed to the shaft is applying the compression to the bellows, but is snug on the shaft by way of a lip seal, and held in place by doubled up set screws.  If the rotor somehow backs off, the bellows will relax and allow some water ingress.

Is this the failure point you are referencing?  If so, there is now a collar (which is also available) to attach to the prop shaft and which holds the rotor snug against the bellows.  I put this on my new prop shaft as security --in the event that somehow the set screws in the rotor backed out.

If not, what is the "potential catastrophic failure point?"   

[Noah]

My worry would be a cracked/torn bellows. It seems like an added complication. Plus, running the burp hose seems like extra work. The traditional log hose seems sturdier. I am a bit of a traditionalist in this regard and my current system has worked well on several boats I have owned (so far), so I am sticking with simple.

[Jim Hardesty]

It seems like an added complication. Plus, running the burp hose seems like extra work. The traditional log hose seems sturdier. I am a bit of a traditionalist in this regard and my current system has worked well on several boats I have owned (so far), so I am sticking with simple.

I agree.  Properly aligned engine, good cutlass bearing and properly adjusted packing is for me.  I keep a kitchen sponge under the packing nut and the water evaporates before getting to the bilge.  But then I'm in fresh water, if I was in salt water and the bilge smelled may change my mind.
Jim

[Ron Hill]

Breaking : I agree with Noah, if you have a ruptured bellows (for what ever the reason) you'll be looking for a travel lift!!   

A thought

[WBev]

I'm no expert on the C-34, but if you have a deck stepped mast the PSS seal makes sense to me.  My Pearson has one, trouble free 7 years of ownership, but we replaced it mid this season as the PSS' age was undetermined.  As of this summer, you could specify no vent on the bellows and keep it the original way.  We chose to run the vent tube and on that boat it was not complicated. We also had a new shaft made, and new flanges, and new cutlass bearing, for little extra cost based upon my conversation with PYI/PSS.

For a keel stepped mast, like my C-34, I chose to stick with standard box, and will be putting in the recently received GFO packing as recommended.  It, too, had been maintenance free until I had the other misfortunes and put the shaft out of alignment.  However, it did add water to the bilge regularly.