Shaft packing size

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firstbase

firstbase

Guru
Joined
Nov 6, 2016
Messages
1,644
Location
United States
Vessel Name
Black Eyed Susan
Vessel Make
Grand Banks 42' Classic
Going to repack both shafts, never done it before. In the water. GB 42' w/ FL 135's and 1 1/2" stainless steel shaft. Packing gland, sorry no pics, is the type with two tightening nuts, one inboard, one out. Want to have the packing material on board when I do it but not sure of the size. From what I read a good guess would be 1/4" or 3/8". Anyone disagree with that estimate? West Marine is close but trying not to leave in the middle of the big event.

Don't want to start a packing material war but WM sells GTU Gore and PTFE packing material. Should I go with one over the other (he asks thereby starting the war). WIthout any comments I think I would choose PTFE as, if I remember correctly, GTU is graphite which can possibly cause corrosion issues? Any comments appreciated and a classic meme from RTF would just take the cake. :)
 
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200w.gif
 
Can't help you with size, but having strips of cloth to wrap around the shaft & jam against the flow of water, plus 1" by about 1' strips cut from a bicycle inner tube to tightly tie & hold the cloth in place does wonders for slowing the flow of water to a trickle.

It's much easier to concentrate when it doesn't sound like the ocean is trying to fill your boat :eek:
 
Great tip on the rags and the old bicycle inner tub trick to slow the flow.

West Marine is pretty good about taking stuff back. If you’re not sure, I’d be inclined to get a couple of sizes and return the wrong one.

Also, if you have an old, long, thin flat head screwdriver, you might find some benefit from bending the tip around into a sort of flat head hook. Very handy for reaching up inside the gland nut to extract the old packing.
 
Now THAT's a classic meme...so proud. :) Thanks guys. Here is an online pic that shows the type I have although much older of course. I'm not really concerned about the water coming in as it seems it would be easy to shove something in there and tighten up the bolts some to slow it down if something was amiss. Will also have someone else with me as well.
 

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MurrayM said:
It's much easier to concentrate when it doesn't sound like the ocean is trying to fill your boat :eek:
Click to expand...

My wife says that's who she feel every time we go out. OK, it wasn't my wife, it was me.
 
Larry M said:
We replaced the PTFE with Gore and it has worked as advertised. Here’s a comparison.

https://www.gallagherseals.com/blog/gore-gfo-fiber-vs-graphiteptfe-packing/

If you can undo the gland without sinking the boat, get a few drill bits and slide those between the collar and the shaft to determine the correct size of the packing. I think 3/8” is to big. Our 2” shaft uses 1/4”.
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Thanks Larry, good tip which I had forgotten. For the record, taking things back to WM is one of my best skills. I think 1/4" is the smallest they make. Probably wouldn't hurt to get up to 1/2" although no way is it that big. I think the calc for length needed is 14 times the shaft size so I need 20"-24" for each shaft if I can get 4 rings in there.
 
Greetings,
I'm still of the thought that the two tightening nuts should be locked against each other on the outside of the flange. That allows the flange to remain snugged up against the packing yet still "float" allowing a very slight amount of movement IF necessary. Thoughts?


NOT like this:


th



But, like this:


th
 
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firstbase said:
Now THAT's a classic meme...so proud. :) Thanks guys. Here is an online pic that shows the type I have although much older of course. I'm not really concerned about the water coming in as it seems it would be easy to shove something in there and tighten up the bolts some to slow it down if something was amiss. Will also have someone else with me as well.
Click to expand...

I have an image of you trying to force it back together and water is just soaking you under high pressure while your reaching for the hammer. Do you have goggles?
 
We have that type of stuffing box with water injection. My 2” shaft takes 3/8” packing.
 
RT Firefly said:
Greetings,
I'm still of the thought that the two tightening nuts should be locked against each other on the outside of the flange. That allows the flange to remain snugged up against the packing yet still "float" allowing a very slight amount of movement IF necessary. Thoughts

My nuts are both on the forward side.
Click to expand...
 
My 1.75" shaft takes 3/4" packing. I found a marine store that took back the 1/4 and 3/8 that I bought at first and sold me the 1/2 and 3/4 that I took for a second try. The minimum contents of a pack contains enough for 3 or 4 wraps. If you buy it off a roll, then you need to know how much to buy and you need to talk to them about their returns policy.
Both nuts on top.
 
sdowney717 said:
I have an image of you trying to force it back together and water is just soaking you under high pressure while your reaching for the hammer. Do you have goggles?
Click to expand...

I have had that image as well but I haven't read about anyone experiencing that type of disaster. My take on it was that yes some water comes in but manageable. Should I keep reading?!?!? One of the reasons I will have someone there who has done these before...
 
U should be fine. I was able to change out entire stuffing boxes in water. From conv to dss. Yes, some water came in[emoji3]
 
A stupid advice but be sure to test your pumps BEFORE starting this work ;)
I want to do the same but on the hard before splashing so also wondering what packing material I should use.

L
 
just did this for first time. remove the existing and buy what you currently have.
 
Maybe get a stiff piece of plastic and cut a strip 1/4" wide. Another 3/8" And another 1/2".
Remove the end and see which strip fits best for the size. Put everything back together (snug) and go buy the packing.
I'd want something with a pointy hook on the end to dig out the old packing too.
Take the packing and wrap it around the shaft somewhere and cut it on the diagonal to fit. At least 3 maybe 4 pieces. Or as many as you can get out of the length of packing.

Then have at it !!
 
firstbase said:
I have had that image as well but I haven't read about anyone experiencing that type of disaster. My take on it was that yes some water comes in but manageable. Should I keep reading?!?!? One of the reasons I will have someone there who has done these before...
Click to expand...

It can spray some water, but not badly, I have done this couple times on my boat too. A deeper hull will have more water pressure on the hull, but you can manage it, your bilge pumps will keep up. The space between prop shaft and shaft log is about 1/8 inch all around at the most.
 
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Packed a few valves and pumps that were secured along time ago, but never a shaft on a boat so nothing technical to add re a boat shaft. Figured it would be best to haul to do this, especially if your first time, but sounds like others think it’s manageable. Cutting the proper lengths and Getting the packing in there correctly takes some practice IMO, so you may want to practice beforehand if you have never done it. Good luck.
 
If you want to know the packing size, look at the photo posted in #7. Measure the diameter of the protrusion on the compression piece ... subtract the shaft diameter and divide that by 2. That will be the packing size. You can gain ease of installation of new packing by lightly hammering down the thickness so it will slide into the housing.

You will be fighting water coming through the packing gland as you remove the old packing. Your packing is internal on the stern tube end and can be a real pain to remove. (some packing systems use a nut with the packing in the nut and the flow from the stern tube can be blocked as referenced previously) It is best to have your new packing strips cut to size and ready to reinstall before removing the old. Most packing glands I have worked on use 3 strips but ??
 
Thanks for all the comments. The guy who will be with me is a marine mechanic and has done them in the past. Otherwise I would leave it alone. However, I think I really need to have it done as I am getting squealing from the shafts after tightening to stop some more than normal dripping. Dripping is now normal or what you guys describe as normal. Sound/squeal is definitely from shaft but no overheating of stuffing box or shaft when it is happening. I can't find any evidence of when packing was last changed so figure I should redo, start all over. The boat was just pulled this past November for bottom job, replace seacock, etc. Dont want to pull it just for this.

New mental picture...me standing on dock next to boat which is now sitting on the bottom. I'm mumbling to no one in particular... "Shoulda had it pulled."
 
firstbase said:
Thanks for all the comments. The guy who will be with me is a marine mechanic and has done them in the past. Otherwise I would leave it alone. However, I think I really need to have it done as I am getting squealing from the shafts after tightening to stop some more than normal dripping. Dripping is now normal or what you guys describe as normal. Sound/squeal is definitely from shaft but no overheating of stuffing box or shaft when it is happening. I can't find any evidence of when packing was last changed so figure I should redo, start all over. The boat was just pulled this past November for bottom job, replace seacock, etc. Dont want to pull it just for this.

New mental picture...me standing on dock next to boat which is now sitting on the bottom. I'm mumbling to no one in particular... "Shoulda had it pulled."
Click to expand...
Are you going to use the Gore fiber?
Do not use the old style flax packing.
It drips lot, can run hot and score shafts, it just is inferior stuff nowadays.

Over 10 years ago, I used Gore GFO marine packing on my old scored dripping shafts, and it has been perfect ever since. I tightened it up about 3 times.
Prior owner who used the old flax packing could never stop the shafts from spraying lots of water, was constantly adjusting the packing, and worried about it too. When I got the boat, there was a steady spray of water soaking everything down there.
 
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The first time I’d ever seen a packing nut was when we first pulled our boat on the hard the first summer we had it.

The previous owner had made a note in the maintenance log for what size packing he used, so I bought that and installed it while on land. Since I’d never done it before, I didn’t know it was too small.

When Badger was back in the water it dribbled continuously from the stuffing box without the shaft even turning.

Luckily I hadn’t thrown the garbage away and fished out the old packing to get the right measurement. This is when the idea about strips of cloth and strips of bicycle inner tubes to stem the flow came from.

One thing I learned from doing it in the water was to find out just how little the packing nut had to be tightened, which really surprised me. Kept an eye on it for the rest of the summer and tightened it slightly a few more times to get the dripping right.

If yours goes anything like mine it’ll be unnerving, but straightforward.
 
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repacking shaft glands.

i have just done this on my trawler yacht. To get the size of the packing, simply measure the diameter of the part of the gland that acts as the packing piece. Take away that diameter from the shaft diameter and you have the packing material size /2.
Are you going to take out all of the old packing? There is a special tool with a screw at the end which makes this easier. Have the new packing ready in the correct lengths. I usually just wind the packing round the shaft several times and then cut with a very sharp cutter at an angle of 45 degrees to the shaft. You don't want the packing to butt up with square ends.
I then usually hammer the packing a little to get it flatter.
Pull out the old packing (it is not necessary to remove it all if you do not want to as you are in a risky situation).
Once you are ready, push the first piece of packing into the gap between the shaft and the housing and push in the metal device which will put pressure on the packing and push it into the gap as far as you can, to get room for the next piece. The piece where the packing joins should be opposite the butting part of the first packing if you are putting in only 2 pieces but at 120 degrees if you are putting in 3 pieces.
Tighten as necessary and then run the shaft so that you can see if it drips. Better to let it drip at first then tighten it to the point where it just stops.
Best of luck. If you get everything prepared you should have no problem.
 
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