Should I repack the stern gland of a newly purchased secondhand boat?

[Gybe Ho]

Another CWDF member is clucking nervously as my re-launch date approaches and I have delayed posting this question.

 

Given a just purchased secondhand narrowboat boat still ashore post survey, should I repack the propshaft stern gland regardless? The boat has a standard bronze greaser and I have yet to burrow my way to the end of the engine compartment to eyeball the stern gland.

 

The surveyor was happy with the propshaft after inspecting it and giving it a good shove. No freeplay can be felt.

 

To avoid the inevitable confusion, by "repack" I mean extract the old square wax wadding and replace setting the 3 section of wadding 120 degrees apart.

 

My boat has about 10 years usage by engine hours and there will have been little static battery charging engine hours.

[Kingdom Isambard Brunel]

1 hour ago, Gybe Ho said:

Another CWDF member is clucking nervously as my re-launch date approaches and I have delayed posting this question.

 

Given a just purchased secondhand narrowboat boat still ashore post survey, should I repack the propshaft stern gland regardless? The boat has a standard bronze greaser and I have yet to burrow my way to the end of the engine compartment to eyeball the stern gland.

 

The surveyor was happy with the propshaft after inspecting it and giving it a good shove. No freeplay can be felt.

 

To avoid the inevitable confusion, by "repack" I mean extract the old square wax wadding and replace setting the 3 section of wadding 120 degrees apart.

 

My boat has about 10 years usage by engine hours and there will have been little static battery charging engine hours.

Depends how far the pusher is in already. If its well out, no, else stuff what you want.

[Gybe Ho]

20 minutes ago, Kingdom Isambard Brunel said:

Depends how far the pusher is in already. If its well out, no, else stuff what you want.

 

There must be some ambiguity in how I phrased the question. Repacking the pusher is a job that I hope can be done as needed post launch. The task I am thinking about, that probably has another description, is repacking the internals of the stern gland at the hull exit. My earlier yachts had lengths of square wadding wrapped around the prop in side the gland. As the plunger pushes in grease the grease is forced around the wadding and propshaft.

 

My most recent yachts had s-drive propulsion hence no conventional propshaft. Maybe stern tube technology has moved on and/or a different design is used on narrowboats.  

[Wafi]

I wouldn't bother unless you specifically know it needs doing. It's easy enough to repack a stern gland with the boat in the water; you'll get dripping water, or at the very worst a very slow trickle, it's absolutely not the gushing you get when you remove something like a log transducer. In fact, on most narrowboats it's probably all of a foot underwater, so it may not even drip very much. You'll also know immediately that it's watertight, rather than having yet another thing to check immediately after the boat goes in the water.

Come to think of it, I've never actually repacked a stern gland on a boat that wasn't in the water. If you need a bit more confidence and can bear the inane commentary, there are probably gazillions of YouTube videos of people repacking their stern glands whilst afloat.

 

Edit: The stern gland on my boat (35-year old WFB) is exactly the same as the ones I've seen on various sailing boats with straight propshafts.

Edited July 3 by Wafi

[Kingdom Isambard Brunel]

19 minutes ago, Gybe Ho said:

 

There must be some ambiguity in how I phrased the question. Repacking the pusher is a job that I hope can be done as needed post launch. The task I am thinking about, that probably has another description, is repacking the internals of the stern gland at the hull exit. My earlier yachts had lengths of square wadding wrapped around the prop in side the gland. As the plunger pushes in grease the grease is forced around the wadding and propshaft.

 

My most recent yachts had s-drive propulsion hence no conventional propshaft. Maybe stern tube technology has moved on and/or a different design is used on narrowboats.  

No body repacks the stern  gland at the hull exit. Its all internal, pusher into the stern carrier which contains the bearing sleeve, there is nothing beyond that.

[Russ T]

Typically the stern gland is packed with stern gland packing. The adjustable pusher, pushes on the gland packing. When it runs out of adjustment, it's time to change the packing. You can bodge it by adding a further packing ring, but it's preferable to dig it out and renew it. Here is a pic of mine with the adjustment bolts removed

Edited July 3 by Russ T

[TheBiscuits]

4 minutes ago, Wafi said:

You'll also know immediately that it's watertight, rather than having yet another thing to check immediately after the boat goes in the water.

 

I was about to post exactly this.  I've seen badly done packing on the hard that didn't get noticed in the excitement of crane back in day ...

[Tony Brooks]

21 minutes ago, Gybe Ho said:

 

There must be some ambiguity in how I phrased the question. Repacking the pusher is a job that I hope can be done as needed post launch. The task I am thinking about, that probably has another description, is repacking the internals of the stern gland at the hull exit. My earlier yachts had lengths of square wadding wrapped around the prop in side the gland. As the plunger pushes in grease the grease is forced around the wadding and propshaft.

 

My most recent yachts had s-drive propulsion hence no conventional propshaft. Maybe stern tube technology has moved on and/or a different design is used on narrowboats.  

 

Repacking the stern gland is where you remove the old packing (presumably what you call square wadding) rings and repack with new, as you describe, with the joints at 120 degree intervals. That is exactly what KIB was describing. The pusher, on many narrowboats, is the thing that pushed on you "wadding". What you call repacking the pusher, I have no idea, unless you are talking about refilling the greaser.

[Gybe Ho]

3 minutes ago, Wafi said:

 

it's absolutely not the gushing you get when you remove something like a log transducer. In fact, on most narrowboats it's probably all of a foot underwater, so it may not even drip very much.

 

 

My pulse rate jumped up the moment I read this as I recalled all the times I told myself "don't rush, ignore the bucket per minute inflow of water... now carefully locate the log back in the tube by touch and don't cross thread the plastic parts. Phew done, time for beer".

[Gybe Ho]

11 hours ago, Russ T said:

Typically the stern gland is packed with stern gland packing. The adjustable pusher, pushes on the gland packing. When it runs out of adjustment, it's time to change the packing. You can bodge it by adding a further packing ring, but it's preferable to dig it out and renew it. 

 

Ok thanks now I can picture the setup. Does this sound right?

1. Whenever the engine has been engaged to turn the prop turn the greaser following engine shutdown.
2. A few times a season refill with grease. The frequency of which will be dependent on the degree of compression applied by the packer and the age of the packing wadding.
3. Very occasionally nip up the packing pusher to apply more compression on the packing rings (wadding) as needed.
4. Exceptionally replace the packing rings preferably while out of the water. Do this ideally before the pusher reaches the end of its adjustment (push) range.

 

Having got that sorted in my head, I hope, my prelaunch obligations are (i) check the greaser is not empty (ii) inspect the packing pusher to ensure there is scope for further adjustment i.e. the packer is not at its limit of extension.

 

Happy to edit this post if I am using the wrong names for the parts involved.

Edited July 4 by Gybe Ho

[Russ T]

44 minutes ago, Gybe Ho said:

 

Ok thanks now I can picture the setup. Does this sound right?

1. Once a day turn the greaser.
2. A few times a season refill with grease. The frequency of which will be dependent on the degree of compression applied by the packer and the age of the packing wadding.
3. Very occasionally nip up the packing adjuster to apply more compression on the wadding as needed.
4. Exceptionally replace the packing wadding.

Having got that sorted in my head, I hope, my prelaunch obligations are (i) check the greaser is not empty (ii) inspect the packing adjuster to ensure it is not at its limit.

 

Happy to edit this post if I am using the wrong names for the parts involved.

1. Turn the greaser when you stop running the engine (assuming it has been in gear) until the dripping stops.

 

2 Refill the greaser when it is running low, I. E when the handle has been screwed in to its limit. Either remove  the top and apply grease, or remove the top, and the tube and fill from the bottom depending on if it will come off.

 

3. Adjust the pusher when the drips become too frequent. The gland should be warm but not hot after adjustment, and you should be able to turn the shaft by hand. (see Tony B's website)

 

http://www.tb-training.co.uk/10sgear.htm#bmn31

 

4. Replace the packing when the pusher has no more adjustment.Or perhaps when it has got so old and hard that its not doing its job.

 

Not sure I would be brave enough to change it while afloat, but I know people do.

 

When we had a new weed hatch welded in, the boat was held in the water still attached to the crane and checked for leaks prior to the yard removing the strops. I am sure the same could be done for the packing. The same could be done with a slip trolley. Not sure about a dry dock though.

 

Ultimately though, whether you change it whilst you are out will be dependent on packing availability of the correct size and type (measure the gap with a steel rule or drill bit), and how much adjustment you have remaining. Again, measure it.

 

I said bolts earlier, though I think in reality, they are studs with lock nuts

 

 

Edited July 3 by Russ T

[Wafi]

1 hour ago, Gybe Ho said:

My pulse rate jumped up the moment I read this as I recalled all the times I told myself "don't rush, ignore the bucket per minute inflow of water... now carefully locate the log back in the tube by touch and don't cross thread the plastic parts. Phew done, time for beer".

Removing the log transducer is one of the classic ways to terrify a neophyte - right up there with pushing your luggage trolly down the escalator at Zurich airport "for a laugh" (spoiler alert: it's even less scary). A mate of mine managed to elicit a full-on scream from his girlfriend when he pulled out the blank on a mooring and shouted that the boat was sinking.

 

Drill bits should be better-publicised as precision measuring devices; in the right situation they're unbeatable.

 

 

 

[zenataomm]

Repacking your stern gland ...
Chucking out your anchor  ...
Changing your gas cylinder ...
Saying "Yes dear" ...
Depositing oodles of cash in your bank account ...
 

Are all things you should consider doing if you have the evidence it is necessary so to do.
Otherwise don't waste your time, effort or money.

[nicknorman]

58 minutes ago, Gybe Ho said:

 

Ok thanks now I can picture the setup. Does this sound right?

1. Once a day turn the greaser.
2. A few times a season refill with grease. The frequency of which will be dependent on the degree of compression applied by the packer and the age of the packing wadding.
3. Very occasionally nip up the packing adjuster to apply more compression on the wadding as needed.
4. Exceptionally replace the packing wadding.

Having got that sorted in my head, I hope, my prelaunch obligations are (i) check the greaser is not empty (ii) inspect the packing adjuster to ensure it is not at its limit.

 

Happy to edit this post if I am using the wrong names for the parts involved.

Yes. Be aware that the packing comes in different sizes and you can get graphite-loaded or normal. Check the position of the pusher/stud length protruding and make a judgement call as to whether to repack. Since it is much easier to do this out of the water, and cheap, I’d suggest doing it anyway if it’s more than about 1/2 worn.

[nb Innisfree]

I've never repacked while afloat but if I did I would first wrap lots of clingfilm around the shaft via the weed hatch to stop water ingress. 

[Machpoint005]

24 minutes ago, nb Innisfree said:

I've never repacked while afloat but if I did I would first wrap lots of clingfilm around the shaft via the weed hatch to stop water ingress. 

 

I've never thought of that. What a good idea! 

 

 

(Does it work?)

 

 

[ditchcrawler]

52 minutes ago, nicknorman said:

Yes. Be aware that the packing comes in different sizes and you can get graphite-loaded or normal. Check the position of the pusher/stud length protruding and make a judgement call as to whether to repack. Since it is much easier to do this out of the water, and cheap, I’d suggest doing it anyway if it’s more than about 1/2 worn.

Mine is PTFE loaded packing 

[MtB]

I think I'd prefer graphited...

 

 

[TheBiscuits]

1 hour ago, nb Innisfree said:

I've never repacked while afloat but if I did I would first wrap lots of clingfilm around the shaft via the weed hatch to stop water ingress. 

 

36 minutes ago, Machpoint005 said:

 

I've never thought of that. What a good idea! 

 

(Does it work?)

 

A well greased rag wrapped tightly around the propshaft via the weed hatch is more traditional.  And sticks better than wet cling film.

 

A bucket under the gland and a working bilge pump are soothing, an assistant on standby with a wet vac is luxurious.

 

 

Edited July 3 by TheBiscuits
Stupid mobile phone

[gatekrash]

2 hours ago, Gybe Ho said:

 

My pulse rate jumped up the moment I read this as I recalled all the times I told myself "don't rush, ignore the bucket per minute inflow of water... now carefully locate the log back in the tube by touch and don't cross thread the plastic parts. Phew done, time for beer".

Have you not done the plastic freezer bag trick ?

 

Place blanking plug in freezer bag. Attach freezer bag over log stub inside boat and tape the neck of the bag tight. Undo the transducer through the bag so that it ends up inside the freezer bag with the blanking plug. Bag fills with sea water, but it doesn't shoot up your arm and into your face. Grab blanking plug through the bag and reattach it to the log stub. Remove bag. Hey presto, only one freezer bag full of water in the bilge and none spraying everywhere. 

 

Having said that, the latest log on my sailing boat has two loose hinged flaps that are flush with the sides of the transducer tube, as you pull the transducer out the water pressure pushes them closed and you only get a trickle into the boat anyway. Very clever !

[Wafi]

15 minutes ago, TheBiscuits said:

an assistant on standby with a wet vac is luxurious.

I can quite imagine, but what about the stern gland?

[Gybe Ho]

1 hour ago, ditchcrawler said:

Mine is PTFE loaded packing 

 

£339 for 8 meters ouch.

 

I would hope to use say 0.5m every 3? years. Presumably as the packing works its way down the distribution chain it is available in smaller lengths?

[Gybe Ho]

10 hours ago, nicknorman said:

Yes. Be aware that the packing comes in different sizes and you can get graphite-loaded or normal. Check the position of the pusher/stud length protruding and make a judgement call as to whether to repack. Since it is much easier to do this out of the water, and cheap, I’d suggest doing it anyway if it’s more than about 1/2 worn.

 

Thanks. This suggests it is possible to get through half the adjustment range over a 2 or 3 year period between haulouts. All depending on cumulative prop revolutions and not overtightening the pusher.

[Gybe Ho]

11 hours ago, Tony Brooks said:

 

Repacking the stern gland is where you remove the old packing (presumably what you call square wadding) rings and repack with new, as you describe, with the joints at 120 degree intervals. That is exactly what KIB was describing. The pusher, on many narrowboats, is the thing that pushed on you "wadding". What you call repacking the pusher, I have no idea, unless you are talking about refilling the greaser.

 

I have revised my 4 bullet point post above to get the terminology right, I initially thought the pusher was the grease container and twiddler.

[Gybe Ho]

8 hours ago, gatekrash said:

Have you not done the plastic freezer bag trick ?

 

 

I never heard of this, my concern would be over getting the plastic bag snarled up with the plug thread, I suppose water pressure keeps the bag extended and out of the way.

 

One of my boats had the flow attenuation flaps inside the log thru hull tube. The extra complexity worried me, I had a vision of weed detritus getting behind the flaps in the closed position.