Newbie questions Stern gland type? Should I keep it? Can it be replaced?

Captain Haddock

Captain Haddock

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Hi Everyone,

I've a bit of a dilemma I'm hoping the panel can help with.

I've had the boat for my first season and it's been great. However, I've had a nagging doubt about the condition of my stern gland and the state of the packing inside. I felt I pushed my luck last season by not checking. However, this season I think I ought to check and if possible replace the rubber hose as I have no idea when this was last done.

It's important to know that I've had no trouble with it all last season although the shaft looked like it was vibrating a lot especially when weed started to grow on it towards the end. I did notice the greaser was turning quite freely after long periods of motoring.

Is this due to the packing being worn and using more grease? Is my (what appears to me) excessive vibration of the shaft down to the rubber hose wearing out? I don't know hence the checking and asking the panel :)

The image below is my stern gland setup.

picture.php


From what I can gather this is a flexible coupling and I assume from where the grease pipe goes into the shaft coupling the big nut at the end is where the packing lives. From what I've read I unscrew the bolt struggle with getting the packing on and then rescrew.

However, on a previous boat I had a deep seal and I just pulled back on the collar let a little water in and job done.

My questions are can this older set up be replaced with something like a Volvo seal?
Does having a flexible hose coupling mean I'm stuck with this setup and I just need to get used to it?
If I am stuck with it how on earth do I get the flexible coupling changed? Do I need to disconnect the shaft (stupid question I guess but I don't know so I'm going to ask anyway!)?
Here's an even sillier question... If I do disconnect the shaft from the gearbox is that going to affect the alignment when I put it back?

I've never tackled this type of job before hence my silly questions :)

Many thanks for taking the time to read all my questions and even more thanks if you are able to help with some suggestions or share your own experience.
 
Nothing difficult about overhauling your existing stern gland. You are right. The packing can be changed by undoing the adjusting ring, removing the old packing - digging it out with a screwdriver or a hooked nail is the usual way. If the shaft looks OK repack with new packing and adjust until the shaft just turns. Job is best done when out of the water and you may need to do final adjustment when you get back in the water and run the engine in gear. Check the hose for any damage, and if it needs replacement you will have to disconnect the shaft from the box, remove the coupling and slide the new hose on. Note that it is a special rubber which you can get from stern gear suppliers. None of this should in itself affect the alignment if you don't move the engine.

You can replace the whole assembly with a Volvo type seal assuming your stern tube is the correct diameter - the dimensions are shown on the Keypart site on all the spares listing for small inboard Volvo engines. Same procedure as replacing the hose, but you need to be sure the shaft is undamaged where the seals fit.
 
Stern gland

Had a friend who acquired a boat with stern gland. He thought that the greaser screw cap was tightened to stop water drip.(which it sort of did) He did not realise that it is the large nut that is tightened to crush the packing so stop water drip while the greaser was to press grease in to lubricate the whole thing. I would imagine that you only replace the packing when you run out of adjustment of the compression nut. I don't know about the hose but good luck olewill
 
I replaced mine with a volvo seal.
They are great and last for years. The 5 years stated is very conservative unless you are using the engine for hours every day.
Remove the coupling from the gearbox and then from the shaft. slide propshaft toward rudder to give enough clearance to remove old coupling and if you are lucky the new seal fits the existing spigot. I was lucky.
Check shaft for staightness by rotating the shaft if out by more than about 3 mm then it will cause a lot of vibration.
 
sarabande said:
do you know Vyv Cox's excellent site, and discussions on stern glands ?

http://coxengineering.sharepoint.com/Pages/Sterngear.aspx
Click to expand...

Yes I have and it's an excellent site. The site certainly shows the "what". However, I'm looking more for the "how" as I'm not sure what to do with this.

Part of me is saying don't touch it's working but the other part of me is saying you don't know about it and now is the time to learn what to do whilst I'm on dry land.

I think I'm leaning towards replacing the packing and monitoring the rubber hose. Although I had no leaks at all during the season which makes me think it must be ok.

When its time to replace the cutlass bearings I think that's when I'd take the opportunity to replace the seal with a Volvo.

Is this the classic case of don't fix what's working?
 
I should start by saying I'm guilty of putting this job off - but NO don't put it off. The hose will degrade over time and even if the outer surface doesn't show it the inside may. A failure will result in rapid flooding - probably faster than I could bail. On the plus side the heart attack from the effort would get me before I could drown!

Replacing the hose and the packing is a relatively cheap maintenance item (although the hose if quite pricey for the right stuff) which most probably do about once a decade. The packing used to require grease, but you can now get PTFE loaded packing which is so slippery it doesn't need additional lube.

Rob.
 
I actually did the opposite ! Started with a mechanical type seal and as this leaked I replaced it with a stuffing box style gland approx. 8 years ago. No regrets. The stuffing box system is an ancient approach to sealing shafts and commonly used on higher speed pumps etc. These can be repacked if the gland packing wears, but on my 1GM10 engine drive unit I have had no need to. I apply grease by one turn on the small greaser every time I run the engine.
My engine is a single cylinder unit and normally runs with a lot of shaft movement. The gland assembly being on a rubber tube connection has behaved very well despite this.
On multi-cylinder engines I would not expect notable/visible vibration or movement on the shaft so I recommend you check your cutlass bearing for wear !
 
If you have access to change the hose without too much difficulty then I think you should. Even if it's fine now, it's obviously going to prey on your mind and you'll be a lot happier knowing it's up to scratch. I did a number of pre-emptive jobs like that when we bought Kindred Spirit, and I don't regret it.

As for replacing with a more high-tech seal; to my mind it depends on the shape of your hull. If you have a flat shallow bilge then it's worth doing what you can to keep it bone dry, otherwise the water comes up to join you when you heel over. A dripless seal is probably a good idea here. If you have a deeper bilge that will keep a little water down where it belongs, then there's no need to change from the traditional box. With teflon packing there's no need to pump gallons of grease into it, and mine just needs a little tweak about once a season. It doesn't drip when the shaft's stopped, and only occasionally when it's turning - when it increases from that then it's time for the tweak.

Pete
 
prv said:
If you have access to change the hose without too much difficulty then I think you should. Even if it's fine now, it's obviously going to prey on your mind and you'll be a lot happier knowing it's up to scratch. I did a number of pre-emptive jobs like that when we bought Kindred Spirit, and I don't regret it.

As for replacing with a more high-tech seal; to my mind it depends on the shape of your hull. If you have a flat shallow bilge then it's worth doing what you can to keep it bone dry, otherwise the water comes up to join you when you heel over. A dripless seal is probably a good idea here. If you have a deeper bilge that will keep a little water down where it belongs, then there's no need to change from the traditional box. With teflon packing there's no need to pump gallons of grease into it, and mine just needs a little tweak about once a season. It doesn't drip when the shaft's stopped, and only occasionally when it's turning - when it increases from that then it's time for the tweak.

Pete
Click to expand...
+1
 
My preference would be to keep the "old fashioned" stuffing box - as others have said well proven technology. But I would definitely replace the rubber hose and use the proper stuff.
You might consider changing the stuffing box to one with 2 studs and adjusting nuts as these are easier to adjust.Have always found T. Norris Marine Equipment. http://www.tnorrismarine.co.uk/ to be very helpful
 
Just an extra reminder to check the shaft. It can get a bit worn where the packing rubs against it. If so can you change the bearing position by using a slightly different length of hose (or fit a different system -eg a Volvo seal)
 
Most of your questions have been answered, so here's a bit of tidying up.

The stern gland, on a rubber hose, follows the shaft. So any movement, vibration, etc that you see there is not caused by the gland itself but by something else. It is often the case that the flanges are not machined perfectly symmetrical, or maybe the engine is moving on its mountings. Try rotating the shaft with the engine not running to check run-out, ideally with a dial gauge but you will be able to see any significant off-centre by setting up a fixed reference point near the stern gland.

Yes, you need to remove the shaft from the coupling but this should not disturb the alignment. Make sure you use the specialist hose - no doubt you have seen the consequences of using general hose on the website. Now would be a good time to check alignment anyway, just in case that is the cause of your vibration.
 
Thank you for all the comments and feedback.

That's it I've decided. Enough with the dithering, the sleeves will be rolled up and the old hose is coming off and the stuffing will be replaced. I'm going to attack this next week I think. I'll post an update on here when I'm done :)

Thanks once again to everyone for sharing their experience it's been very helpful.

I know it'll always be nagging my mind every time I go out so I've got to address it.

I'll also post comparison shots between the old stuffing/new stuffing and old hose/new hose.
 
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