Water injected stern glands

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Polarsailor

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Dear All

My brother has bought a small motor boat that he plans to leave on a drying mud mooring. I am used to stuff boxes on my own boats but this boat has a stern gland with a water injection pipe running from the engine seawater inlet. Ideally I would recommend him to close this sea cock which feeds the engine and stern gland wen not on the boat. Is it OK though if there is no constant feed to the stern gland. Is the water feed to cool the shaft only or is water pressure required to maintain the seal?

Anyone have any thoughts?

Brgds Keiron
 
It is just to keep the seal and cutless cool and water lubricated. Obviously he will have to open the seacock to run the engine so this will also open the flow of water to the stern gland. Probably worth checking whether the inlet has a grid over it as that might get blocked with mud, and there is a means of quickly rodding the inlet if it does get obstructed.
 
Makes sense to close the seacock when not on the boat - why would you want to leave it open? Are you completely sure that the pipe running to the stern gland is actually a water feed - my engine has a water cooled gland and the pipe which "feeds" it turned out to be a vent pipe - it saves me having to burp the gland when the boat dries out.
 
Modulation said:
Makes sense to close the seacock when not on the boat - why would you want to leave it open? Are you completely sure that the pipe running to the stern gland is actually a water feed - my engine has a water cooled gland and the pipe which "feeds" it turned out to be a vent pipe - it saves me having to burp the gland when the boat dries out.
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Vent tubes for PSS and other types of stern gland are fine for relatively slow boats. Most of them seem to recommend that for boats capable of more than about 10 knots a pumped supply should be arranged.
 
I have a water lubricated/cooled stern gland. The water feed does not 'maintain the seal', that will be done with the packing. The water feed is probably lubricated the outside bearing as well. It's a very sensible arrangment. I always close the seacock when leaving the engine (and all the other seacocks).
 
There's a new seal going on as part of the engine replacement on LK. It's a PTFE packed gland that's nearly dripless, it also has a water feed for lubrication, I've never had one before but it's highly recommend because of the long stern tube we have. Is it really necessary to turn off the engine stop cock each time? I never turn the engine one off because it's a pain to get to and frankly I trust the hose not to spontaneously explode :) but does the gland-feed add a potential siphon issue and mad stupid question of the day - is the water coming from the cold side or post cooling - if it's from the cold side doesn't that reduce the amount of cold sea water available to cool the engine in the heat exchanger?
 
No evidence that there is any need to close a seacock when you leave the boat. However some people think it is necessary, but the thing they are guarding against is failure of the hose below the waterline. How common is that? Does make sense however to operate the valve from time to time to ensure it will close properly.

Water intakes are usually oversized and the small bleed to the stern gland is not going to affect the amount of water going to the engine for cooling.
 
Tranona said:
No evidence that there is any need to close a seacock when you leave the boat.
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I beg to differ. My cockpit drain seacocks remain open (except when having a party) and have suffered substantially more barnacle growth than the other 6 which are normally left closed when the boat is not in use. Why filter feeders would want to live up a pipe with no flow I do not understand but the wee buggers seemed to thrive. Also, I have direct knowledge of a boat that filled her bilges, albeit slowly, when the engine water inlet pipe split at the clip at the engine end.
 
awol said:
I beg to differ. My cockpit drain seacocks remain open (except when having a party) and have suffered substantially more barnacle growth than the other 6 which are normally left closed when the boat is not in use. Why filter feeders would want to live up a pipe with no flow I do not understand but the wee buggers seemed to thrive. Also, I have direct knowledge of a boat that filled her bilges, albeit slowly, when the engine water inlet pipe split at the clip at the engine end.
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Equally, I have never routinely closed seacocks in the 40 years I have owned boats - much of that time with boats in the water all year round and have never experienced those problems - although admit I have never had a boat that needed cockpit drains with seacocks. My only leakage has actually been with a seacock that was closed (a cone type) because it was leaking. However it continued to weep even when closed because the cone had worn oval.

Not sure either experience leads to a universal conclusion.
 
If my boat was drying out on mud every tide, I would definitely close all seacocks that didn't need to be open. Having mud pressed up into the pipework can spoil your day.
 
NormanS said:
If my boat was drying out on mud every tide, I would definitely close all seacocks that didn't need to be open. Having mud pressed up into the pipework can spoil your day.
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Do you really thing the mud is going to get past the skin fitting and through the valve to block the pipework?. Surely more important to have a means of rodding as typically even with the valve closed there will be up to 3" of tube downstream of the valve that can fill with mud (or barnacles).
 
Tranona said:
Difficult to set a general rule based on one boat of poor design!
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Obviously the original design brief was sadly lacking - inadequate buoyancy in the stern for drinks parties and no bunks big enough for celebrity 3-somes (would Time Inc be upset if I mentioned the names published in our national papers?) - so unlike the accommodating design of modern fat-arsed Benjenbavs.
 
awol said:
Obviously the original design brief was sadly lacking - inadequate buoyancy in the stern for drinks parties and no bunks big enough for celebrity 3-somes (would Time Inc be upset if I mentioned the names published in our national papers?) - so unlike the accommodating design of modern fat-arsed Benjenbavs.
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Being able to hold drinks parties in the cockpit without soaking the trouser legs of one's guests is definitely a big selling point for a boat. However, if you are sensible and keep your boat in warm climates a bit of water in the cockpit is no longer an issue.

Of course you are in a privileged position to know the names of the threesome (unlike us south of the border) but we know our political leaders' tax details whereas you are denied that pleasure.
 
Tranona said:
Of course you are in a privileged position to know the names of the threesome (unlike us south of the border) but we know our political leaders' tax details whereas you are denied that pleasure.
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Not sure what wee Nicola's tax returns have to do with sea cocks or boats but I confirm she has published hers. Does that mean Nigel has recanted and published his?
 
awol said:
Not sure what wee Nicola's tax returns have to do with sea cocks or boats but I confirm she has published hers. Does that mean Nigel has recanted and published his?
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Not sure Nigel and his financial affairs invite much interest these days, although his expenses and what he paid his wife caused a bit of a stir a few years ago. Anyway there is a better connection between poor cockpit drains and him given his well known habit of drinking with lots of his mates at every opportunity - although he seems to prefer saloon bars.
 
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