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  #1  
Old 04-13-2009
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Stuffing Box Trouble

Ok sorry to start another stuffing box thread but wanted to explain what just happened to me because something isn't right...

Changed the flax packing 4 days ago with the same exact size as what came out - three rings of 3/16 flax packing. Ring insertion went fine and I also had someone who had done it before there to help and guide me. So today the boat went into the water and while at the dock I took my wrenches in and unlocked the locking nut. I had made sure to leave it semi loose as not to over tighten and with the locking nut off I had about a drip every 5 seconds while in neutral and a drip about every 2-3 seconds with the shaft spinning at low speeds(while the locking nut was off/loose). Ok I thought that is good to start and I can always adjust it for less drips later on when it all settles in - well I used 2 wrenches to tighten the locking nut while making sure to leave the packing nut in same position - well no drips - not 1 while the shaft was even spinning at 2100 rpms...After 5 minutes I got nervous, put it in neutral, loosened the locking nut and walla plenty of drips. I then even backed the packing nut even further off just to make sure for my trip to my mooring I plenty of cooling water. At that point I had a steady stream coming in until I tightened it again with the locking nut - again no drips.

So Sorry for the long post but just wanted to make clear what I did. To me it seems that the locking nut seems to be blocking any drippage. Also where should it be dripping from - between the locking and packing nuts or elsewhere? At this point I get no drips when the packing nut is backed off just about all the way while the locking nut is fully tightened. Locking nut slightly loose and plenty of drippage. Also for the trip over (about 30 minutes) I kept checking - no drips but at the same time the stuffing box and shaft never got hot. Any suggestions? Thanks in advance.
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Old 04-13-2009
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Are you sure that your not getting drips?

If you're getting drips that fast while at rest, then spinning should yield much higher rate. Are you sure that your just not flinging the drops all over the engine compartment?

Do this experiment:

Adjust the drip rate to the few drips a minute when not spinning the shaft. Make sure that you do this with the locking nut tight. Go for a ride with the motor running while having someone else drive. Go below and put a piece of Cardboard round the stuffing box, but about 5 or so inches away. See if the cardboard gets wet, if it does, then you're just flinging the water off instead of dripping, which is why you don't see it drip. Also, is the front of the packing nut wet, by front I mean where the shaft enters the nut from the motor side. If so, the water is getting to the shaft and cooling

When locking the locking nut, it is very easy to think that you are not moving the nut, when in reality your moving it also.

DrB
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Old 04-13-2009
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There is also the option of a dripless packing gland.
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Old 04-13-2009
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Quote:
Originally Posted by DrB View Post
If you're getting drips that fast while at rest, then spinning should yield much higher rate. Are you sure that your just not flinging the drops all over the engine compartment?

Do this experiment:

Adjust the drip rate to the few drips a minute when not spinning the shaft. Make sure that you do this with the locking nut tight. Go for a ride with the motor running while having someone else drive. Go below and put a piece of Cardboard round the stuffing box, but about 5 or so inches away. See if the cardboard gets wet, if it does, then you're just flinging the water off instead of dripping, which is why you don't see it drip. Also, is the front of the packing nut wet, by front I mean where the shaft enters the nut from the motor side. If so, the water is getting to the shaft and cooling

When locking the locking nut, it is very easy to think that you are not moving the nut, when in reality your moving it also.

DrB
Thanks for the thoughts but thats the problem...I can't get stuffing box to drip at all with the locking nut tight! For instance I tried backing off the packing nut so that it was just about off and water was pretty much gushing in. As soon as I tightened the locking nut - no drips at all and regardless if the packing nut was moved slightly while tightening it, it was way too loose anyway so it wouldn't have mattered.

Also I do know what you mean about the spray but today my girlfriend was at the helm and I had my had in the engine compartment the whole way with my hand on the stuffing box and I am 100% positive there was no drips or spray for that matter. Its the weirdest thing I can adjust the packing but so that water is either gushing in or I get the perfect few drops a minute but in either position as soon as I tighten the locking nut - no water/drips/spray period.
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Old 04-14-2009
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Another idea

Just thinking aloud here. Are you sure that your are not moving the packing nut when you are tightening the locking nut. Like I said in my first post, it is easy to do even when you think that you are not.

So if I understand you from your posted statements, you can get a decent flow at rest and when the shaft is spinning, but not when the lock nut is brought against the packing nut, correct?

Is this a standard stuffing box set-up (Packing nut, threaded flanged section that goes into the flex tube/bellows, and a lock nut between the packing nut and the bellows) or something different? Does the locking nut also help compact the flax in some way or have a compression seal that seals against the packing nut in some way? This could cause a seal that wouldn't let water out and would be in-line with the observation of drips only when the locking nut is not engaged.

Before the flax was changed, did the SB work with the packing/lock nut properly tightened, just excessively?

DrB
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Dr. B - Thanks for your responses and suggestions, I really appreciate your help. The stuffing box is very normal and just like all the others I have seen. Also there is no special seal or anything on the locking nut. I am careful not to move the the packing nut while tightening but even just to do an experiment for myself, I backed the packing nut so far off so that water was gushing in and then tightened the locking nut and same thing - no water - so even if I did slightly tighten the packing nut - it was so far off that it wouldn't have mattered.

Now where am I supposed to be getting a drip from? Between the packing nut and locking nut or further towards the engine where the shaft enters the packing nut?

Oh and also prior to this change I did observe the correct drip amounts both at rest and with shaft spinning so I know this is not a special stuffing box.
Thanks again
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Old 04-14-2009
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NK25 let's go back

to square one. The water should exit between the shaft and the packing nut. Not the locking nut.

If it is sumthin ie really FUBARed. So I would like you to go to this site by Mainsail. He was gracious enough to share his knowledge ( so I don't have to do it) and do a write up of stuffing boxes along with other stuff. Sort of a Stuffing Box For Dummies approach. Follow his steps and you will have no problems. Re-Packing A Traditional Stuffing Box Photo Gallery by Maine Sailing at pbase.com

Fair Winds

Dave
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Old 04-14-2009
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Hmmmmm:

You said you got three rings in there. How many threads is that packing nut grabbing? Could it be that the packing nut is barely threaded onto the SB and only the locking nut is stopping the flow?
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Old 04-14-2009
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lbdavis makes a good point...

My SB had four rings in it. I know that they are all different, but that could be your problem. If you are able to thread the Packing Nut on four or five turns, you may not have enough material in there. On mine the new material allowed to just get barely one full turn on the nut once the threads were engaged. If your doing more than say two full turns, you're probably material short.

DrB
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Old 04-14-2009
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Did you tighten the packing nut with a lot of force to get the nut on the thread - you might have jammed the packing tight against the shaft. BTW is not the water th counts its excessive heat in the packing gland
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