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Old 07-01-2022, 16:45   #1
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Re-pack stuffing box - How often?

I'm back to my stuffing box obsession. Last season I was having a bit of trouble adjusting it the way I like it and wondered if it's time to repack.

I don't think it should be time - the whole thing was replaced when the engine was replaced, about 250 engine hours ago. On the other hand, that was more than 10 years ago in real time.

Does calendar time matter? How often should I expect to do this?

Thanks for any insights. No, I didn't search for other threads on the subject; am going through a lazy period (we call it "winter" in this region).
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Old 08-01-2022, 05:09   #2
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Re: Re-pack stuffing box - How often?

Well, 250 hours is not that long but 10 years is.

I would say if you're having trouble adjusting it, it's probably time.

Lol, and I'm guessing you feel that way too, but - understandably - you don't want to do it !

I've heard it said it's like reefing - when you first think about it - it's time to do it !!

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Old 08-01-2022, 05:21   #3
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Re: Re-pack stuffing box - How often?

Might it be a good time to get over the obsession and replace the stuffing box with a shaft seal? Then you'll have time to obsess over something else that's more fun.

Stuffing boxes have a wierd status in the world of mechanical devices. The "right" condition for them is a sloppy situation, with the stuffing not quite sealing, and slightly leaking. If you get them to actually do the job of keeping the water out, you've over tightened them. That's easy to do, and then they need adjustment again. Do it a few times, and they need restuffing. If you have any tendency to obsession, as I do, they are a trap for your brain. A shaft seal does the job, doesn't leak, and needs next to zero maintenance. I think that stuffing boxes should be retired wherever possible, even if just for our mental health.
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Old 08-01-2022, 05:44   #4
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Re: Re-pack stuffing box - How often?

If you're thinking about it, just do it! the packing costs maybe $12 to do and is an easy project. maintained a stuffing box is one of the simplest most reliable devices onboard. There's no point in doing anything drastic like switching to a "shaft seal" (Which is a dubious upgrade at best) just repack it
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Old 08-01-2022, 05:52   #5
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Re: Re-pack stuffing box - How often?

Quote:
Originally Posted by OldManMirage View Post
I've heard it said it's like reefing - when you first think about it - it's time to do it !!

I like this analogy.

Last year I didn't have access to the boat until a couple of weeks after the usual launch date; this year I'll probably run out of excuses. Another project, yippee!
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Old 08-01-2022, 06:06   #6
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Re: Re-pack stuffing box - How often?

Consider using goretex. Synthetic packing has an extra step to it but worth it.
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Old 08-01-2022, 07:43   #7
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Re: Re-pack stuffing box - How often?

having a shaft seal stuffing box is wonderful thing .. for sure
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Old 08-01-2022, 08:14   #8
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Re: Re-pack stuffing box - How often?

How often they need attention depends on the specifics of the installation, the packing used, how little water you like to see through it, etc. In other words, there's not really a set time for it, just "as needed".

The newer synthetic teflon and/or graphite loaded packing materials are a good upgrade from the old waxed flax. They last well, but more importantly, they don't need as much water leaking through to keep them sufficiently cool and lubricated. With a synthetic PTFE packing in the stuffing boxes on my boat, it's pretty easy to get them adjusted to where they hardly drip at all once the boat has been stopped for a few hours (just show a little moisture, but very rarely an actual drip) yet they stay cool to the touch at fast cruise (17 kts on this boat).

Personally, I have no desire to own a dripless seal. They're nice when they're working (and they are lower maintenance), but the potential failure modes are significantly more ugly than those of a stuffing box. And there are far more maintenance or failure concerns that can require a haulout to resolve.
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Old 08-01-2022, 08:32   #9
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Re: Re-pack stuffing box - How often?

More than 10 years, I'd be thinking about replacing the stuffing box hose. Check engine alignment at the same time, probably due after 10 years as well.
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Old 08-01-2022, 09:32   #10
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Re: Re-pack stuffing box - How often?

Cracked, and they do, dripless shaft seal can sink your boat. I prefer old-style stuffing box.. never a problem.
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Old 08-01-2022, 09:56   #11
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Re: Re-pack stuffing box - How often?

Adjusting a stuffing box to the way you would like it to perform is anything from finicky to impossible. I have obsessed over mine for years and have come to a simple solution...it's better to have it dripping slightly more than less and pump out the bilge more often. I prefer to have too much flow and know I have cooling and lubrication rather than have to worry about not having enough. I also have a point and shoot digital thermometer gun which I use to check engine temp at different locations on the engine. I use this gun to measure the temp of the stuffing box before starting engine and at various times during operation. This will give you a realistic idea about how hot the stuffing box actually gets and the amount of flow passing through it. I sail in the PNW and find that my stuffing box typically runs between about 45- 54 degrees C. This is not high enough temp to cause damage to the SS prop shaft. Your dishwasher cleans at 60 degrees C.
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Old 08-01-2022, 10:44   #12
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Re: Re-pack stuffing box - How often?

This thread may perhaps be relevant for you?

https://www.sailnet.com/threads/ques...acking.331022/
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Old 08-01-2022, 10:51   #13
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Re: Re-pack stuffing box - How often?

I replace my packing when it gets finicky to get adjusted. The packing is hard. The one thing to remember is to sneak up to the adjustment. The adjusting nut drives the packing into a taper to compress the packing to the shaft. Often once overtightened just backing off the nut may not decompress the packing. I don't worry much about timing the drip. When I think it's right I check temp. On my sailboat it runs barely warm, much cooler than previously mentioned.
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Old 08-01-2022, 11:03   #14
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Re: Re-pack stuffing box - How often?

Like cat4 said but I think of it differently: when you get tired of screwing with it, and still can’t get it right, replace it.

I went through the commotions for years on our previous boat because I was too lazy to replace it after 15 years. Finally got to the magic point and broke down and replaced it. Afterwards it didn’t leak a drop and the shaft was always cold. BTW aligned the shaft too and a new coupler.
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Old 08-01-2022, 12:03   #15
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Re: Re-pack stuffing box - How often?

On my previous boat, I had a stuffing box, the type with the packing follower and two bolts that allowed adjustment. Replacing the packing was an annual event and sometimes more often. This was on a commercial fishing boat which logged about 1000 hrs a year. It was not a handy place to get to to adjust the packing. I saw an innovation on another commercial boat that I adopted. By attaching a fitting to the stuffing box which allows grease to be inserted into the packing the shaft stayed cool and replacing the stuffing not as often. A one quarter in. tubing was run to a grease gun located in the cabin. A daily shot of grease kept the stuffing box from dripping to much and the shaft cool.
On this boat I have dripless seals. This is a pleasure motorsailer. I run a couple of hundred hours a year. And I have replaced the seals once in 15 years. In the water. The choice of what to use is dependent on several variables. How much use, the shafts still turn while you are sailing, the access to the units, and your mechanical aptitude.
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