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Old 05-31-2019, 11:28 PM   #1
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Repacking Stuffing Box

I have a 1999 Mainship 390 which has I believe a 1 3/4" propeller shaft. I am running out of adjustment on the stuffing box which has an adjustment nut on each side of the box, the boat is in the water and I have several questions:
1. Is 1/2" packing the size called for?
2. Would GFO packing be a good choice?
3. Can I get by temporarily, that is until I haul her out in a year or two, with adding a new ring of packing without removing the old?
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Old 05-31-2019, 11:42 PM   #2
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I saw a video stating you can do it by putting plumber putty on the outside but you have to get in the water. Or you can put a rag over the shaft and try to do it quickly.
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Old 05-31-2019, 11:54 PM   #3
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I don’t know about what size you need but my shafts are 2” and take 3/8” packing. You could pull the plate off and see what size drill bit will fit in between the shaft and the log. I suspect it will be a bit less than 3/8”.
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Old 06-01-2019, 07:28 PM   #4
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A stuffing box should not just be blindly tightened and if your running out of room, that makes me a bit uneasy. Pulling out stuffing and replacing is usually an easy job, safely accomplished in the water. If you run into issues, just stuff a little anything in there while you go to the chandler or hardware store. A rag, some paper towels. If the shaft is not turning, just about anything is going to work.

Best to get new packing in there. Come prepared with a couple corkscrew tools. If the packing is baked and hardened from being overtightened, it can be a bit crispy to pull out and it is possible to break a tool. Packing that is old and not hardened will usually come out quite easily. Another hint, if you guess wrong at the perfect packing size, just massage it with a mallet/hammer gently to make it a little thicker, or thinner. You can make any close size work and it will simply cause the overall depth to change just a bit.

Iím not at all a fan of adding a new ring to old packing.

Personally, I prefer gfo.

If you have troubles getting new packing to seal without over-tightening, then inspect the shaft for scoring. Thatís a real possibility resulting from prior over tightening. If the shaft is in good shape, and you put in the new rings at the right shape and size, you should tighten gently at first and creep up on the right adjustment slowly while running a little at a time. If you are starting to get tight and not seeing obvious reduction in dripping, instead of continuing to get tighter and tighter, check whether the shaft is wobbling and the running gear needs alignment. You wonít be able to get a stuffing box to perform right unless the running gear is in alignment and otherwise good shape. This ultimately is what often leads to over tightening and baked packing.
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Old 06-01-2019, 08:08 PM   #5
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Just add more packing rings.
Prepare the packing material by wrapping it around the shaft, cutting it to the proper length.
Perhaps 3 rings.
Back the packing gland, moving it down the shaft, away from the prop. Add one new ring at a time, tighten the packing gland pushing the new ring in. Start the engine, rotate the shaft slowly. Do the same with the 2nd ring and maybe the third ring.... Each ring is pushed on the with the packing gland.
Dont worry about a vast amount of water, it wont happen.
After adding all the necessary packing, take the boat for a ride, making the final adjustment while underway. It is supposed to leak a drop or 3 to keep the packing material cool.
If you are unsure of yourself, seek help from another boater. It is simpler and less scary than one may fear.
IF I recall correctly, the packing gland should be in about 1/3 of the total distance.
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Old 06-01-2019, 11:07 PM   #6
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You might find this very recent thread helpful:

-- Packing change while in water?
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Old 06-02-2019, 03:42 PM   #7
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Thank you for all the solid information. You have been most helpful.
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Old 06-02-2019, 11:57 PM   #8
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Packing box

Quote:
Originally Posted by ghost View Post
A stuffing box should not just be blindly tightened and if your running out of room, that makes me a bit uneasy. Pulling out stuffing and replacing is usually an easy job, safely accomplished in the water. If you run into issues, just stuff a little anything in there while you go to the chandler or hardware store. A rag, some paper towels. If the shaft is not turning, just about anything is going to work.

Best to get new packing in there. Come prepared with a couple corkscrew tools. If the packing is baked and hardened from being overtightened, it can be a bit crispy to pull out and it is possible to break a tool. Packing that is old and not hardened will usually come out quite easily. Another hint, if you guess wrong at the perfect packing size, just massage it with a mallet/hammer gently to make it a little thicker, or thinner. You can make any close size work and it will simply cause the overall depth to change just a bit.

Iím not at all a fan of adding a new ring to old packing.

Personally, I prefer gfo.

If you have troubles getting new packing to seal without over-tightening, then inspect the shaft for scoring. Thatís a real possibility resulting from prior over tightening. If the shaft is in good shape, and you put in the new rings at the right shape and size, you should tighten gently at first and creep up on the right adjustment slowly while running a little at a time. If you are starting to get tight and not seeing obvious reduction in dripping, instead of continuing to get tighter and tighter, check whether the shaft is wobbling and the running gear needs alignment. You wonít be able to get a stuffing box to perform right unless the running gear is in alignment and otherwise good shape. This ultimately is what often leads to over tightening and baked packing.
I think what Ghost stated is correct. If after repack ing and it still leaks much, the the shalf might not be too straight due to gear alignment. Gears go through pressure and heats that overtime can be out of alignment which leads to shalf not spinning straight which leads to leads to more water entering.
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Old 06-10-2019, 07:44 PM   #9
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Also, the shaft could be scored if you have been tightening it willy nilly.
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Old 06-10-2019, 08:51 PM   #10
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DO NOT use carbon shaft seal. It is for pumps etc and will destroy your shaft log or the shaft.
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Old 07-30-2019, 12:06 PM   #11
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which size should i get?

Quote:
Originally Posted by Dream Quest View Post
1. Is 1/2" packing the size called for?
My Own Mainship 350 is leaking now when prop not turning which size packing should i get?
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Old 07-30-2019, 12:17 PM   #12
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Quote:
Originally Posted by Mainshiptom View Post
My Own Mainship 350 is leaking now when prop not turning which size packing should i get?
My 1999 350 has a dripless. Interesting that they released both a 350 and a 390 in 1999. Mine must have been released EARLY in 1999, prior to the model name change.
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Old 07-30-2019, 02:14 PM   #13
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Quote:
Originally Posted by Mainshiptom View Post
My Own Mainship 350 is leaking now when prop not turning which size packing should i get?

Have you tried tightening the gland nut a turn or so. Thats its function!!! Every so often as wear takes out packing you just tighten the net a bit till it just stops....but dont tighten it down too tight, its not a bolt, or you could score the shaft!!!!
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Old 08-01-2019, 03:08 AM   #14
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which size should i get?

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Originally Posted by jimisbell View Post
Have you tried tightening the gland nut a turn or so. Thats its function!!! Every so often as wear takes out packing you just tighten the net a bit till it just stops....but dont tighten it down too tight, its not a bolt, or you could score the shaft!!!!
Thanks for the advice , I did tightened the screws and leak has stopped but i would like to have new packing on board and would be interested if anyone can advise on size? i have a single caterpillar 3116
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Old 08-01-2019, 03:11 AM   #15
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350/390

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Originally Posted by Shrew View Post
My 1999 350 has a dripless. Interesting that they released both a 350 and a 390 in 1999. Mine must have been released EARLY in 1999, prior to the model name change.
Maybe mine is a 390? or a 350 how do I find out? in the HIN number?

There is no where to say what boat it is?
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Old 08-01-2019, 09:07 AM   #16
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I would not change boats just for the stuffing box, its cheaply changed. BUT, and this will cause some discussion, I prefer a stuffing box to a dripless any day as my neighbor almost lost his boat with a dripless that got some sea weed in it.
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Old 08-07-2019, 03:20 PM   #17
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Quote:
Originally Posted by Dream Quest View Post
I have a 1999 Mainship 390 which has I believe a 1 3/4" propeller shaft. I am running out of adjustment on the stuffing box which has an adjustment nut on each side of the box, the boat is in the water and I have several questions:
1. Is 1/2" packing the size called for?
2. Would GFO packing be a good choice?
3. Can I get by temporarily, that is until I haul her out in a year or two, with adding a new ring of packing without removing the old?
Just done mine so its a single shaft and I used 1/4" packing
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Old 08-07-2019, 04:34 PM   #18
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I have never removed old packing. Just keep adding more for years. Usually 2 or three rings. I dont know where the old goes and I dont care......probably where the elephants go to die and where all the short stubby pencils and short pieces of solder go.
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Old 08-07-2019, 05:45 PM   #19
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The size of packing material is determined by measuring the outside diameter of the shaft and the inside diameter of the stuffing box and dividing the difference by two. Your local yard should be able to verify this for you. Don't guess the size or just measure the shaft because you may not have the same brand name stuffing box as another boat with the same shaft size.
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Old 08-07-2019, 10:21 PM   #20
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Quote:
Originally Posted by Eagle Pursuit View Post
The size of packing material is determined by measuring the outside diameter of the shaft and the inside diameter of the stuffing box and dividing the difference by two. Your local yard should be able to verify this for you. Don't guess the size or just measure the shaft because you may not have the same brand name stuffing box as another boat with the same shaft size.
I agree 100%
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