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Old 03-15-2014, 04:59 PM   #1
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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.
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Old 03-15-2014, 05:08 PM   #2
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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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Old 03-15-2014, 05:34 PM   #3
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Stuffing Box

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Do you have a picture? I've read this through a few times and still do not understand the problem or solution.
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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Old 03-15-2014, 05:48 PM   #4
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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.
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Old 03-15-2014, 05:59 PM   #5
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Originally Posted by N4061 View Post

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
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?
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Old 03-15-2014, 06:00 PM   #6
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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....
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Old 03-15-2014, 06:02 PM   #7
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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.
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Old 03-15-2014, 06:09 PM   #8
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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.
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Old 03-15-2014, 08:20 PM   #9
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....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...
This is kind of where I am on this.

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Old 03-15-2014, 08:26 PM   #10
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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?
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Old 03-15-2014, 10:45 PM   #11
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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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Old 03-15-2014, 11:37 PM   #12
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Quote:
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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.
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..!
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Old 03-16-2014, 06:36 AM   #13
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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.

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Old 03-16-2014, 08:18 AM   #14
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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.
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Old 03-16-2014, 05:42 PM   #15
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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

Lets try this with a PDF of the spreadsheet
Attached Files
File Type: pdf N3522 Stuffing Box PDF.pdf (92.2 KB, 133 views)
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Old 03-16-2014, 05:54 PM   #16
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OK
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Old 03-16-2014, 06:05 PM   #17
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Lets try this with a PDF of the spreadsheet
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.
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Old 03-16-2014, 06:07 PM   #18
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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.
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Old 03-16-2014, 06:23 PM   #19
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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.
Base upon my schematic what or where would you conclude is the problem? Thanks
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Old 03-16-2014, 06:31 PM   #20
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... 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.
An excellent idea.

Dave
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