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Thu, December 07 2023, 19:24Login ] [ Contact Forum Admin ] [ Main index ] [ Post a new message ] [ Search | Check update time | Archives: 123[4]5678910 ]

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Date Posted: - Friday - 03/19/10 - 8:52pm
Author: Randall, Murre, M31
Subject: Replacing Packing Gland Material

My “dripless” packing gland has been dripping for some time now. I have tried to tighten it over the years since installation (four, I think) without success, and to my eyes the nut and visible threads appeared very corroded, so I assumed the packing needed replacing. I’d never done that job before. Given that the packing nut is in a spectacularly difficult place to reach and that Murre is in the water, I called for help from a local pro named Ken.

What follows is a report of today’s work in case you have a similar situation and feel similarly hesitant.

1. I unloaded the entirety of the port cockpit locker. Everything. On Murre the only access that allows any reasonable leverage on the nut is from here. The lucky sod who’s given this job must lie on his back, feet stern, head down, and reach in, embracing the fuel tank like it’s a lover.

2. BIG NUT LOOSENING TIP, WORTH THE PRICE OF ADMISSION AND THEN SOME – Before anything else, before even showing that he’d brought a wrench, Ken crawled into position and tapped the gland nuts with a regular sized carpenter’s hammer. He tapped the corners of the packing nut and the lock nut in their respective loosening directions (the packing nut loosens counterclockwise, the locknut the opposite). He tapped the “corner” of each nut gently but repeatedly. This exercise lasted about 10 minutes. Ken said that bronze is an “immortal metal” and that bronze on bronze simply does not corrode. The tapping loosens gunk on the threads and “has only failed me once.” I held my breath.

3. Next he handed me a large set of channel locks and had me torque the packing nut (I was holding a flashlight on the scene from the starboard side) while he held the locking nut. It took almost no pressure to back off the packing nut. I was amazed.

4. Water flow from the opened gland only equated to about a quart a minute, not the gusher I’d imagined, and the bilge pump handled this just fine.

5. Before backing the nut up the shaft, Ken used a small chisel to scrape off the rust and salt from the prop shaft. All boats have this layer of gunk on the shaft near the nut, said Ken, and if you don’t scrape it off, the packing and the nut will get stuck as they are eased away.

6. For digging out the old packing material, Ken used what looked like a dentist’s tooth-cleaning tool, a thickish needle with a right-angled bend at the point. He pricked around inside feeling for the bitter end of the packing, which was recognized by a little extra give when pulled. Once found he held his “hook” in place and twisted the nut, essentially unscrewing the tight and somewhat hard packing material from its location. He did this three times for the expected three pieces of packing.

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[> Replacing Packing Gland Material -- Randall, - Friday - 03/19/10 - 8:53pm

7. For replacement stuffing, we used ¼” GTU (Murre’s shaft is 1 1/8” diameter), an entirely synthetic weave of Gortex impregnated with Teflon. It looks like gooey chain mail rope and feels like snake skin. The plan was to do the first and third ring with GTU, but to use a paste of moldable packing called SYNTEF in the middle. This stuff looks like sticks of green putty and is essentially grease mixed with Teflon microfibers.

8. Ken cut the GTU to size based on one of the old pieces he felt had fit most snuggly. The two bitter ends must match up. One on Murre, he noted, was obviously too short.

9. Next he greased the GTU piece lavishly with the grease from the SYNTEF kit.

10. Inserting the GTU into the nut was difficult. The threads on Murre’s packing nut were very sharp, and so Ken used a small metal punch tool to help push the stuffing into place. Then he screwed the nut down by hand to ensure it seated properly.

11. Once the nut was backed off again, Ken shaped the SYNTEF putty to the approximate size and length of the GTU piece and then stuffed it in the nut.

12. This was followed by a repeat of step 10, and it was equally difficult, but once stuffing the outer ring of GTU in place had revealed a few threads, Ken hand tightened the nut into place, and the leaking suddenly dried up to nothing.

13. Ken had applied some of the SYNTEF grease to the packing nut threads before synching it in place for the last time with channel locks and promised it would not seize up again.

14. Just after I he left, I ran the engine in gear for 15 minutes. The nut got very hot and squeezed out a significant amount of packing. I called Ken who said the squeezing out of excess packing was normal for the first run, but the heating up was not. “The nut should not be hot to the touch. That’s too tight. It won’t hurt the shaft or nut, but prolonged heating will shorten the life of the packing. Let it cool. Run the engine again, and if it’s hot again, back the nut off a tiny bit, just 1/16 of an inch. That little bit will create a lot of space in the nut. I ran the engine again later and the nut did not heat up.

So, that’s today’s learning.

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[> [> Packing -- Doug Wilson, - Saturday - 03/20/10 - 1:18am

I used the Gortex packing, I have heard some say it scores the shaft, but after three years there was no scoring.
Went back to flax packing in November, without the no drip stuff, no drips.
One thing that's handy is a laser thermometer, a safe way to check the packing. Once it's broken in, should be good. On leaving San Carlos, the packing nut got up to 155 F, but cooled to the same temperature as the shaft after an hour. Right now the shaft temp runs about 86F and the packing nut about the same.

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[> Packing Gland -- Mark, M31, #62, - Saturday - 03/20/10 - 11:18am

Another great write-up by Randall, nice pics. Been so long since I've replaced my packing I didn't even know they made "dripless packing". Here's a site with somemore good info on the subject http://www.wptinc.net/wpt_tech.html. Thanks again Randall, yet another thing to add to the "to do" list :)

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[> Material advances and time of job -- Randall, - Saturday - 03/20/10 - 8:54pm

Forgot to mention the job took about three hours. I was really pleased I'd chosen to be taught this one as it would have taken me all day. For example, I wouldn't have known to look for three rings of packing, nor would I have ever thought of the nut removal trick.

Thanks Mark. I felt such relief over getting the job done I just had to write it up. Funny how some jobs can really knaw at you. Have been feeling fairly discouraged of Murre this winter. Gloomy, wet weather, a rewiring job that goes on and on, and a leaky stern gland had left me feeling blue. But I woke the morning after this job with affection again for the old girl.

Speaking of material advances, I mentioned to Ken that when I had the packing replaced last (four/five years ago?) I'd been told it was a drippless install. "Funny," he said, "packing material has undergone a revolution in the last two years w/GTU and Teflon grease, etc. I can't imagine them calling it 'drippless' back then."

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[> [> Packing Rudder Post -- Kathy M32#3 Shadow, - Sunday - 03/21/10 - 11:25am

The rudder post also has three strands of packing flax, which after 25 years was surprisingly discovered when the deck was being taken off. After 40 years it looked in good shape, so don't be to concerned. I'm learning as I sail along.

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[> Excellent Report... -- Paul M31 #106, - Monday - 03/22/10 - 10:18am

The pictures added the third dimension. Thanks for sharing with us.

A few more weeks and I will be united with my Mariner when I sail her down from Maine to her new home and tackle some of thise items myself.

The suspense is killing me.

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