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Are these nuts meant to be tight?

Daltonia

By Daltonia
in Boat Building & Maintenance

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Daltonia Contributor

Daltonia

Posted
Posted

The two nuts arrowed below are very loose (I can turn them with my fingers).

1. Are they meant to be tight?

2. Are there, perhaps, meant to be two nuts on each thread, rather than one on each?

 

The reason I ask the second question is that I have found a single nut of the same size on the bilge floor, beneath this part of the propellar shaft, and can only think it came from here. Many thanks for any help.

post-25277-0-59500000-1474211288_thumb.jpg

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Tony Brooks Veteran II

Tony BrooksDonate to Canal World

Posted
Posted

The nuts should not be tight ad the one you found is almost certainly a locknut that was tightened against the existing nuts when the correct stern gland adjustment was set. There should be a locknut for the other stud as well.

 

The two nuts should be tightened until you have between one and two drips a second from the gland after a days cruise (or the drip just about stops but a drip of water or grease is forced form the front of the gland when the greaser is used). You should still be able to turn the shaft by a hand on the coupling. If you can't the gland is probably too tight. The gland may run warm but never hot.

 

Once the gland is adjusted fit the lock nuts or use self locking nuts.

 

 

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furnessvale Influencer

furnessvale

Posted
Posted

The two nuts arrowed below are very loose (I can turn them with my fingers).

1. Are they meant to be tight?

2. Are there, perhaps, meant to be two nuts on each thread, rather than one on each?

 

The reason I ask the second question is that I have found a single nut of the same size on the bilge floor, beneath this part of the propellar shaft, and can only think it came from here. Many thanks for any help.

They are adjusters for the stern gland and should not be "tight" although a bit tighter than fingertight is normal.

 

They should have locknuts on them so that they can be tightened when necessary to (almost) stop the stern gland from dripping.

 

Too tight will overheat the gland, too slack will leak water into the boat. For myself, one drip from the gland every 10 seconds or so is about right. Catch the drips in an old margarine tub.

 

George ex nb Alton retired

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MoominPapa Veteran II

MoominPapa

Posted
Posted

No, they're not meant to be tight, and yes there should be two nuts on each thread, locked against each other. The nuts you have, when tightened, push the packing piece into the gland to compress the gland packing. This should be done just enough to stop the gland leaking excessively but not enough to make the shaft hard to turn, or prone to overheating in use. The exact force may vary, but it will be nothing like enough to lock the nuts; for that a second nut is run down the thread and the two are tightened against each other.

 

Cheers,

MP.

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J R ALSOP Proficient

J R ALSOPDonate to Canal World

Posted
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I have to disagree, my stern gear is 37years old, it has never been repacked, nuts are nipped up so i can roll the shaft with my foot, I use grease on a regular basis, morning, noon and night. I have only had about two pints "of drips" through the packing in all that time. It is open to inspection at any time, i'm at Alvecote at the moment, Park head next weekend.

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Tony Brooks Veteran II

Tony BrooksDonate to Canal World

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My stern gland also does not drip and never has since we bought the boat about 17 years ago but it does have an Aquadrive so the shaft is always in perfect alignement and I take great care never to over-tighten it. However the traditional approach is one or two drips a minute with the greaser stopping the drips.

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by'eck Veteran

by'eck

Posted
Posted

The two nuts arrowed below are very loose (I can turn them with my fingers).

1. Are they meant to be tight?

2. Are there, perhaps, meant to be two nuts on each thread, rather than one on each?

 

The reason I ask the second question is that I have found a single nut of the same size on the bilge floor, beneath this part of the propellar shaft, and can only think it came from here. Many thanks for any help.

 

I suspect from reading other posts that you are getting confusing advice on this thread. The nut or nuts should be tight to each of the studs they are screwed onto, so that the relatively light pressure placed on the adjusting flange for the stern gland is locked. The adjustment is made equally each side so the flange remains parallel to the stuffing box and with the minimum pressure to stop any dripping, commensurate with being able to turn prop shaft by hand. The adjustment is then usually secured by locking two nuts against each other on each of the studs.

 

It appears on your photo that at some time the gland as been overpacked causing the adjusting flange to sit further out, and leaving a minimal amount of stud to fix two screws on. One solution would be to use a single self locking (nylock) nut on each stud that once adjusted would achieve the same goal.

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bizzard Veteran II

bizzard

Posted
Posted (edited)

Super, thanks for the very useful replies. I'll replace them with self-locking nuts (which, unfortunately, are only sold in bags of 100 at Screwfix, so I'll have 98 spare...).

The studs that the nuts screw onto are VERY often not proper studs at all but just lengths of threaded rod. Proper studs have a slightly raised blank section in the middle with threads on either side of it. These studs should be tightened up on the tube flange before sliding the pusher on and screwing the nuts on. The studs can be tightened up with a proper stud undoer-doerupper or a good pair of Mole grips or monkey grips. Failing to do this or if you have just plain threaded rod on each side they can unscrew which makes self locking or two lock nuts a bit pointless. If you haveproper studs make certain that they are tight. If you have threaded rod you may be able to get nuts on the back side of the tube flange to keep the threaded rods tight. If not remove the threaded rods, clean scrupulously the threads on the rods and the female threaded holes and apply Loc-Tite thread lock to them, screw em in and let them cure before fixing the pusher back on with the lock nuts.

 

ETA. If it has threaded rods and they seem to be nice and tight someone may have Loc-tited them in already.

Edited by bizzard
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Scholar Gypsy Veteran

Scholar Gypsy

Posted
Posted

The studs that the nuts screw onto are VERY often not proper studs at all but just lengths of threaded rod. Proper studs have a slightly raised blank section in the middle with threads on either side of it. These studs should be tightened up on the tube flange before sliding the pusher on and screwing the nuts on. The studs can be tightened up with a proper stud undoer-doerupper or a good pair of Mole grips or monkey grips. Failing to do this or if you have just plain threaded rod on each side they can unscrew which makes self locking or two lock nuts a bit pointless. If you haveproper studs make certain that they are tight. If you have threaded rod you may be able to get nuts on the back side of the tube flange to keep the threaded rods tight. If not remove the threaded rods, clean scrupulously the threads on the rods and the female threaded holes and apply Loc-Tite thread lock to them, screw em in and let them cure before fixing the pusher back on with the lock nuts.

 

ETA. If it has threaded rods and they seem to be nice and tight someone may have Loc-tited them in already.

 

That's a good point - I learnt about this issue a few years ago when I realised that one of the threaded bolts was removing itself from the flange.

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bizzard Veteran II

bizzard

Posted
Posted (edited)

 

That's a good point - I learnt about this issue a few years ago when I realised that one of the threaded bolts was removing itself from the flange.

Indeed. The reason why I mentioned this again was that I came across this AGAIN yesterday afternoon whilst servicing and fitting a new alternator to a BMC 1.8 in an ex Alvechurch hire boat. I happened to notice the pusher was out a long way with the gland dripping rapidly. Threaded rod again unscrewed itself. I was stuck for time so just screwed them in and burred the rear end of them a little with a hammer. to stop them unscrewing again.

Edited by bizzard
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