N3522 Stuffing Box

The following post was made on the Nordhavn Owners site and I thought would be of interest to others. I'm also interested to hear from others on this subject.

So after two days on the hard N3522 was back in the water today and I received the call to plan to take her home at 3:30pm. Left work early, drove to my marina, jumped in cab to other side of the bay and as I was walking into the yard I get the call from the yard owners son advising we still are not getting water to the coupling. By this time I was walking into the yard and seen him on his cell. He explained even with the new cut-less bearing being installed (sticking out a little more then normal to allow for a little more water flow and ease of future removal) confirming the shaft is perfectly centered and plenty of water reaching up to the coupling they cannot get water past the coupling even after shortening the packing material up to 1/4 - 1/2" and putting the boat in reverse. I confirmed the stuffing box and coupling are original. using the process of elimination the only thing to do is remove the coupling and machine it down so it is not rubbing against the shaft and allows water flow. This makes sense to me since this is the point of water blockage. So the boat stay at the yard and I got to take another taxi back to my car just in time to fight Friday night traffic home. Trying not to get stressed out but at $1K per day this is getting expensive and not going over well with Mary who loves the boat and wants to get back onboard.
Looking at this as the margarita glass being half full, once we get this figured out we should have the coolest running stuffing box on the west coast. So here is todays question, does a semi-displacement boat with a 370HP Yanmar running at various RPM's run hotter (stuffing box) than say a N40, N43, N47, (you get the picture)? I wouldn't think so and stuck in the 30 degrees above water temperature as the normal temperature.


Another data point that somewhat confirms the yard position is that temperatures using the inferred gun start out at 87 degrees at the shaft housing / transom interface then increase as we move forward up to the maximum temperatures at the brass coupling. Even the rubber around stuffing box was 20-30 degrees cooler then the coupling only a few inches away which would indicate a very close fit not allowing water to pass through.

Do you have a picture? I've read this through a few times and still do not understand the problem or solution.

Stuffing Box

Northern Spy said:

Do you have a picture? I've read this through a few times and still do not understand the problem or solution.

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No picture close up. The best I can explain is water enters through the cutless bearing through the propeller shaft up to where the coupling pushes against the packing then appears to stop. Theory is to open up the clearance between the coupling and the shaft to allow water to pass over the shaft and exit the front the coupling. Hope this helps. thanks

John

New packing can run hot until it is broken in. On mine, it took probably 5 running hours. It ran hot even if gland was loose. All by itself it magically started running cool with no leakage.

N4061 said:

No picture close up. The best I can explain is water enters through the cutless bearing through the propeller shaft up to where the coupling pushes against the packing then appears to stop. Theory is to open up the clearance between the coupling and the shaft to allow water to pass over the shaft and exit the front the coupling. Hope this helps. thanks

John

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I think I get it and I'll rephrase back to you.

Water flows past the new cutlass bearing through the stern tube and up and into to a freshly packed stuffing box. No water is dripping out of the gland follower or spud nut and that is yours or the yards concern. The mechanic either removed a ring or two of packing or cut a packing ring short. (I don't quite get this part.) Still no drip. So you are boring out the spud nut or gland follower to increase the clearance between it and the shaft.

Is that correct?

The packing should have nothing to do with water and the cutless bearings.

One keeps the water out of the boat and somewhere's aft of it are one or more cutless bearings that keep the shaft in line.

Northern Spy's evaluation seems correct so far....but like him unsure what the problem is...just the packing overheating?

Water never gets to the coupling in any boat hopefully....I just reread your post for the 3rd time and the terminology is wrong enough...I have no idea what you are trying to ask...ignore all before....

The stuffing box nuts are way too tight? This may be the wrong answer, but it comes with a wee tale which goes like this;

The previous owner of our boat was deceased, so we replaced the stuffing by using the size last noted in the maintanence log. When the boat went back in the water, there was water "dribbling aggressively" from the stuffing box.

Turns out he had changed things, but must have been feeling unwell so never put that in the log. We didn't know we had bought a smaller size stuffing material than was needed, because we'd never done it before.

So, as complete rookies, we had to get the right size of stuffing material and replace it with the boat in the water...it's a disconcerting sound to hear the ocean rushing into your bilge

We had strips of rags at the ready to wrap around the shaft and stuff back towards the prop, and strips of cut up bicycle inner tubes to hold it all in place. Once it was wrapped up, hardly any water came in and gave us a chance to work at a relaxed pace.

The right size stuffing material was put in, the wrapping taken off, then the nuts were tightened until the rush slowed to a trickle, then to a very slow drip, and we kept an eye on it once in a while just to be sure.

I was amazed at how little the nuts had to be tightened to get a drip every thirty seconds or so while underway, and hardly drip while stopped. The stuffing box barely gets warm underway.

That's what makes me think the nuts are way too tight.

I read it again. I certainly hope they didn't pack it by wrapping the packing around the shaft in a big spiral. Bad practice.

Anyways it could be that the packing was tightened prematurely and it is air bound.

Packing doesn't "un- compress" very well. It only compresses. A rookie mistake is to take up the packing too quick. I like to pack shafts loose and gradually tighten up so as to always maintain a healthy leak rate until it is run in and then can be snugged up until the desired drip rate.

....I just reread your post for the 3rd time and the terminology is wrong enough...I have no idea what you are trying to ask...

Click to expand...

This is kind of where I am on this.

Dave

I too am thinking this might be as simple as an air lock. Unless you let the air out, the water will never fully flood the shaft tube. Perhaps back off the packing nuts and let some water flush through to burp the air out, then go from there?

Greetings,
Mr. N. Do NOT allow the yard to machine anything! Have them repack the stuffing box and have it done by someone who knows what they're doing. Mr. NS is correct packing doesn't un-compress very well. The advice you've been given thus far is spot on.

RT Firefly said:

Greetings,
Mr. N. Do NOT allow the yard to machine anything! Have them repack the stuffing box and have it done by someone who knows what they're doing. Mr. NS is correct packing doesn't un-compress very well. The advice you've been given thus far is spot on.

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I agree, it sounds like this is just a standard stuffing box, and this yard might be so used to only fitting and servicing dripless seals they are are trying to find a solution to a non-existent problem here. I would have thought just backing off the packing nut or nuts a wee bit, running the boat, keeping an eye on the stuffing box temp, and it will probably all sort it self out. I have noticed both times I have had my box stuffed with this new teflon based packing, the box is vitally dripless unless actually running. I feel very negative towards the yard machining surfaces to actually create a leak - does not compute..!

Is this a new problem or a continuing problem?Any signs of wear on the shaft where it interfaces with the packing. I know a fellow who had the wrong size packing installed in his boat and was fortunate to catch it before it got more exensive.

Sent from my iPhone

I agree with others. If it worked before it should work again so don't do any machining. What has changed is who is doing the work. Get some different help. It sounds like a lack of experience on their part or perhaps they are taking advantage of your concern to generate some additional work for themselves.

Attachment

N4061 said:

No picture close up. The best I can explain is water enters through the cutless bearing through the propeller shaft up to where the coupling pushes against the packing then appears to stop. Theory is to open up the clearance between the coupling and the shaft to allow water to pass over the shaft and exit the front the coupling. Hope this helps. thanks

John

Click to expand...

Lets try this with a PDF of the spreadsheet

OK

N4061 said:

Lets try this with a PDF of the spreadsheet

Click to expand...

So with 50% of packing removed, water still will not flow?

Remove 100% of packing and water will come through. Machining gland inside diameter is not recommended.

Greetings,
Mr. N. I agree with Mr. bglad. It worked before for X years so what did the yard do to change the geometry? Get in touch with Nordhaven and see what THEY say. I'd be quite surprised if there was a problem with their original design and instillation. Something doesn't add up here. Again, I wouldn't let the yard do ANY machining what-so-ever. Once the material is gone, it's gone.

Ski in NC said:

So with 50% of packing removed, water still will not flow?

Remove 100% of packing and water will come through. Machining gland inside diameter is not recommended.

Click to expand...

Base upon my schematic what or where would you conclude is the problem? Thanks

RT Firefly said:

... Get in touch with Nordhaven and see what THEY say. I'd be quite surprised if there was a problem with their original design and instillation.

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An excellent idea.

Dave

Greetings,
Packing material too tight. Remove all and re-pack properly. My $.02.

N4061 said:

Base upon my schematic what or where would you conclude is the problem? Thanks

Click to expand...

My best guess is the packing was installed too tight, or not allowed to break in. That causes gland to run hot and not drip. They took out 50% of the packing and water still did not come out. That is because 50% of the packing is still in there, and apparently is still sealing. So take that packing out too, and you should get flow.

Next, put packing in loose, and let it dribble. With shaft rolling, gradually tighten until drip slows. If shaft gets hot, put in neut and let it cool, repeat. Not uncommon for gland to get hot with new packing. It needs to be carefully adjusted and allowed to break in.

See my earlier post that described my experience.

Nordhavn Input

magicbus said:

An excellent idea.

Dave

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I spoke with Dan (co-owner) of PAE Nordhavn (they know us well) and he was not sure himself what could be causing the problem. We are using one of the best yards in San Diego (well respected for over 60 years) and they handle Nordhavns from time to time but this is not a Nordhavn specific problem. Based on original owners input, the box always showed in 100's (not sure how high) which is leading me to think this may have been an issue from day one and he never realized it. It may have become worse after he had it repacked since the older packing material was well worn out. This wouldn't be the first time in history that something went unnoticed for many years by the owner then when the boat or car changes owners it is noticed.

I'm still waiting to hear from everyone what temperatures you register off the coupling at cruise speed with this type of stuffing box? Thanks

To answer your question specifically I don't recall seeing packing glands running much more than ambient water temperature. That is a gland that has been run in.

One thing I do not see on your diagram is a cooling water line. Many (in fact most) glands I see have those. They are usually taken from the main engine raw water cooling system somewhere. Possibly you are missing yours or it is clogged? If you don't have one that could be your problem. If you do then it may not be flowing properly due to a clog somewhere.

I have attached a picture of one in a 44' DeFever I recently surveyed. The cooling line is the copper tubing. The wire is for bonding the fitting.

Good on you for your persistence in resolving this although I don't think the stainless, bronze or flax cares much about 100 degrees F. That being said it is a substantial difference if you are starting with 50 degree F water...

N4061 said:

I spoke with Dan (co-owner) of PAE Nordhavn (they know us well) and he was not sure himself what could be causing the problem. We are using one of the best yards in San Diego (well respected for over 60 years) and they handle Nordhavns from time to time but this is not a Nordhavn specific problem. Based on original owners input, the box always showed in 100's (not sure how high) which is leading me to think this may have been an issue from day one and he never realized it. It may have become worse after he had it repacked since the older packing material was well worn out. This wouldn't be the first time in history that something went unnoticed for many years by the owner then when the boat or car changes owners it is noticed.

I'm still waiting to hear from everyone what temperatures you register off the coupling at cruise speed with this type of stuffing box? Thanks

Click to expand...

Hmmm. I'm still waiting for the PDF. Must be because I'm on a phone. Will look at it when I get near a computer.

I've got exactly zero experience with packing glands like this, but I'll venture a theory anyway.

I think you are starting out with the packing too tight. Entrapped air is preventing the tube and glad from ever fully flooding which would explain why there has been no sign of sea growth up there. With no water there is no lubrication and things run hot. It's probably been this way since day one.

Question: The previous owner said the temp was always 100ish. Was he ever getting drips out of the seal, or was it always dry?

As a starter, I'd start with the packing VERY loose and encourage active water flow initially to ensure the tube is completely flooded and bled of air. Then tighten just enough to control the water flow, but keep it going at a higher than normal rate for some initial break-in time. Monitor the temp to see if it's now closer to sea temp. Assuming it is, then over time tighten up to whatever drip rate you want.

After all that, if the temp does back up then I'd guess that air is getting back in there an/or you have too little water circulation. Creating more clearance may help, but if the problem it air introduction an entrapment, then I don't think more clearance will solve the problem. I'd then start thinking about a vent line like in the Defever picture to allow the air to self-bleed. If that doesn't work then you could consider using the vent line to actively flush water from the packing gland back out through the shaft tube. This is commonly done on higher speed boats to get enough water flow.

bglad said:

To answer your question specifically I don't recall seeing packing glands running much more than ambient water temperature. That is a gland that has been run in.

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Thank you for your post. My N40's and this boat do not have an extra cooling line as shown in your picture. I plan to watch the technican remove all the packing and see what happens. If we are still not getting water then I have to conclude something else is fitting too tight. Fortunately the shaft is fine and no damage anywhere but this is a strange one to figure out. Especially the owner reports low 100' as remembered temperatures, that's just a little warm for me. I know most people wouldn't stress as much as I am but I am a little of a perfectionist when it comes to boats. Not a good sickness to have but has made for safe boating over the years!

john

First of all, this is nearly the easiest application for packing. The shaft speed is low. SAY 1.5 inch shaft turning at 1500 rpm is only 589 fpm (relatively slow). The medium is clean cool water. The differential pressure is low. There is not much axial play. There is little radial movement. This is not rocket science.

Lets start with terminology because I'm still a bit confused. The fibreglass housing is typically called the stern tube. What you are calling a coupling is commonly called the stuffing box, packing box, or packing gland. The shaft goes through it and it provides an annular cavity in which the the packing goes into. The piece that is you adjust the packing compression with the two nuts on the studs is called the packing follower or the gland follower.

Do you have a large diameter hose between the stuffing box and the stern tube? Or is the stuffing box rigidly mounted to the hull? The reason I ask is that the packing boxes with a chunk of hose are (somewhat) self-aligning.

Personally, I'd do as the others said and pull out the packing and replace. It may have been packed incorrectly (particularly when you say they cut a half in off or so) and needs a burp. I'm a big fan of GFO packing. It should last many, many years in a boat. I've used in in 4" shafted 1,800 rpm continuously running pumps for years.

A good tutorial can be found here. There are lots of other out there.

I won't repeat what others have said, but here are a few other things you may consider.

Is the packing gland cocked? Measure the flange ears to stuffing box distance on both sides.

Is the packing the right size? It should go in rather easily.

Misalignment. You had the cutlass bearing changed. Is the new one straight? Was the old one worn? When you have the packing out, you can measure the concentricity of the shaft in the stuffing box.

100F is nothing to a box like that. Once it wears in a bit it will run cool down.

I think the thing to keep in mind here, John, bearing in mind your perfectionistic tendency, (which I share, and often have to discipline myself over, especially when it relates to boats), is this is just a stuffing box. Stuffing boxes are rude, crude, but frightfully effective, and through a range of conditions. I think you are lucky yours does not rely on forced cooling, (nor does mine), as these types never suddenly completely fail, and as I posted before, is often dripless when not turning after a new pack, but still runs quite cool, and 100F is less than 50C, so just tolerable hand hot, and not really a worry, as Northern Spy said. If water is getting up to the packing coupling that's really all that matters. The small drip one often sees is certainly not enough flow to create meaningful circulation, just one small sign it is there. Keeping tabs on the temp for a bit will do that. Rotation of he shaft should ensure a movement of water around and back down the shaft just by differential expansion. But a check the repack was not too over-tight, as others have mentioned, and that the packing follower is square to the box, does make sense. This should be at no further charge to you in my opinion also.

I would conclude the schematic is wrong...never seen or read about an arrangement like that.