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Stern gland help required could you look at this pic


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Hi all , I have been having issues with water in the bilge , first I found a engine hose leaking, stopped the leak sorted I thought , umm no . Then I found the elbow on the shower drain was broken , sorted I thought, umm no . Then someone says that I should check the stern gland , sure enough it was dripping they said undo the two nuts screw in the gland and retighten the nuts . All good except when I touched the nuts they were loose and the gland was moving up the shaft, it does not screw in , it is like a top hat shape and was making its way down the prop shaft as the bolts were undoing . I pushed it back tightened the nuts pumped in some grease , no leak , prop turns all good . Question is then do I have a different type than most and have I done the right thing . On the picture below you can see by the grease mark how far it was undone .

 

 

20130522_2001121_zpsb97ac5a1.jpg

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Yes you've done the right thing, but it won't last all that long from the look of it. I think the gland needs re-packing.

 

Any easy job for a local marine engineer bod to do it for you. Or do you fancy having a bash yourself?

 

MtB

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That is a completely standard arrangement for a modern stern gland - the usual kind.

 

However the moveable part should be compressing several rings of stern gland packing down into the void into which it goes, and up against a solid lip in the non moveable part.

 

If there were adequate packing present, you would expect there to be a gap between the two "oval" shaped plates, but it looks as if you tightening the nuts has either brought them completely together, or within a whisker of it, with no further adjustment possible.

 

That means there absolutely is not enough packing in there - either there never was, or it has in some way degraded, broken up, or otherwise gone missing. You will not be able to make further adjustment, I think.

 

It needs at least some more rings added, (which may suffice), although as there is no clarity about what is in there, the correct procedure would be to completely replace anything that is tere completely with new.

 

It can be a DIY job, and can be done in water, but it depends on how confident you feel about a situation where quite a bit of water might (or might not) come in when you do it.

 

FWIW, I have done two boats recently, with no water coming in at all on either, but I can't guarantee that will always happen.

 

EDIT:

 

This post shows replacement of packing in a somewhat larger gland on our tug, but the principle is the same. In our case some of the packing was undersized, probably just intentionally, as the depth it packs into is far deeper than on a modern gland, and I think it had been added just as a spacer to stop so much of the correct size being needed - perhaps they had run out?

Edited by alan_fincher
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Your adjusting nuts are gradually unscrewing themselves, you need another nut on top of the adjusting nuts to lock them together.

 

Not so sure about that. It's hard to tell due to the grease but they look like 'Nylock' locking nuts to me.

 

MtB

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Your adjusting nuts are gradually unscrewing themselves, you need another nut on top of the adjusting nuts to lock them together.

They are so covered in grease I couldn't convince myself if they were some kind of Nylock self-locking type or not.

 

At first I thought they were, but now I think you are right, they are just ordinary nuts, and need another one on to lock threm.

 

That said....

 

1) One of our boats didn't have lock-nuts on and they never moved - although I've added some now.

2) There still isn't currently enough packing in there, whether you lock the nuts or not!

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Not so sure about that. It's hard to tell due to the grease but they look like 'Nylock' locking nuts to me.

 

MtB

Could be, if so they are probably worn and/or grease is providing too much lubrication for the plastic inserts. Personally I prefer ordinary nuts locked together in this application.

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Thanks all ,l am happy to have a go at it now I know it can be done in the water , Where is the best place to buy the packing ? Is it something a marina would stock ? Next to find shallow part of canal and switch on all bilge pumps lol.

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Its very common for the threaded studs to unscrew instead of the nuts, indeed judging by the spare length of the studs this side of the nuts it looks like that's what's happened here. The nuts look like self locking nuts although not quite certain because of all the grease. If the studs are loose the nuts need running back or off and the studs screwing back in tight into the back flange with a stud tool or small grips or stilsons tightening them close up to the back flange so as no to damage the used part of their threads. If they are not screwed tight into the back flange they will quickly loosen again.



Thanks all ,l am happy to have a go at it now I know it can be done in the water , Where is the best place to buy the packing ? Is it something a marina would stock ? Next to find shallow part of canal and switch on all bilge pumps lol.

ASAP supplies are very reasonably priced and their online service is fast.

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Cheers Bizzard looks like I needs to get the flange out to find which size rope/packing I need , at least ill find out how much water is going to come in ohmy.png

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Its very common for the threaded studs to unscrew instead of the nuts, indeed judging by the spare length of the studs this side of the nuts it looks like that's what's happened here. The nuts look like self locking nuts although not quite certain because of all the grease. If the studs are loose the nuts need running back or off and the studs screwing back in tight into the back flange with a stud tool or small grips or stilsons tightening them close up to the back flange so as no to damage the used part of their threads. If they are not screwed tight into the back flange they will quickly loosen again.

 

ASAP supplies are very reasonably priced and their online service is fast.

If the studs are just plain threaded studding with no plain section of stop shank on them I'd get two proper studs with the shanks, if not you may be able to lock the studs with nuts at the back of the back flange by screwing the studs right trough enough. ''Those gland back flanges stud holes usually are open at the back'', if enough room, if not withdraw the studs completely clean all the threads scrupulously with spirit and loc-tite them with thread lock or loctite-retaing compound.

 

If the studs are just plain threaded studding with no plain section of stop shank on them I'd get two proper studs with the shanks, if not you may be able to lock the studs with nuts at the back of the back flange by screwing the studs right trough enough. ''Those gland back flanges stud holes usually are open at the back'', if enough room, if not withdraw the studs completely clean all the threads scrupulously with spirit and loc-tite them with thread lock or loctite-retaing compound.

If you have an 1.1/2'' shaft the packing is most likely to be 5/16'' but not always, yes pull the packing pusher out and measure the depth.

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The studs are fixed into the rear part , almost like hub studs pressed in from the rear, nuts are nylock but I will clean everything and replace if necessary , I think what has happened is that the flange has come loose a little and the previous owner has just kept pumping grease in, the packing is then not held in place and has broken up or disintegrated where the shaft has been turning . Hopefully there is still enough packing to hold the water out whilst I add the new , and hopefully this may be the end to my bilge water , there was a lot in there last night checked tonight and still dry but she has not been in gear today so will have to wait and see.

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The studs are fixed into the rear part , almost like hub studs pressed in from the rear, nuts are nylock but I will clean everything and replace if necessary , I think what has happened is that the flange has come loose a little and the previous owner has just kept pumping grease in, the packing is then not held in place and has broken up or disintegrated where the shaft has been turning . Hopefully there is still enough packing to hold the water out whilst I add the new , and hopefully this may be the end to my bilge water , there was a lot in there last night checked tonight and still dry but she has not been in gear today so will have to wait and see.

Yes just make sure the studs are tight in the back gland flange, if not do one or the other of what I said. Cut your new packing rings to size first so ready to fit. Make sure the bilge pump is working ok, turn the greaser a good bit before changing the packing, get all the old stuff out first, not much water should trickle in with no packing present.

Edited by bizzard
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To find packing size you can measure the diameter of that collar, and subsract that of the shaft from it, then divide by 2.

 

Example:

 

Collar 2 1/8" diameter

Shaft 1 1/2" diameter

Difference 5/8"

Packing 5/16" (8mm)

 

But another trick is to just withdraw the moveable part right back, then insert drill shanks until you find the largest that will fit. If an 8mm drill shank will pass down the slot, but 9mm will not, then you need 8mm packing.

 

It will distort slightly, but not enough to work reliably if you use the wrong size, (e.g. 6mm will not work well if correct size is 8mm - even though a professional engineer did this to one of our boats, and swore blind it would change shape enough to work fine :banghead:)

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When Earnest was a year old, I replaced the packing with PTFE packing. I finally replaced that last year...not bad for 10 years and what it has been through.

Again when Earnest was a year old, I replaced the brass studs (slightly longer, as I had the room) with stainless steel and standard size stainless nuts, so much easier to tweak than the thin brass nuts originally supplied.

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Good advice not to over tighten, take the nuts up as far as you can by hand then spanner them one flat at a time on each side so that the stuffing box is being taken up equally. Do that until the shaft won't turn. At that point undo them a little (again one flat at a time on each side) until the shaft turns freely. Run up the engine with the gearbox engaged and keep feeling the shaft to make sure that it isn't overheating, if it is then undo them equally a little more and repeat, otherwise you could get excessive wear on the shaft. I saw one that looked like an hourglass once.

Ged

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