Stern Gland

Freedom35 said:
I recently started athread re Volvo Penta's which is an engine installed on a Freedom 35 I have now purchased, and your advice on starting it was spot on, not having experienced one previously.

Following running the engine stern gland seal is leaking water which will be repaired.
I researched the gland type and this is the result:

The Volvo seal is entirely constructed from rubber, combining the hose that attaches to the stern tube with lip seals that prevent leakage of water into the boat. An internal bearing is water lubricated while the lip seals need to be greased occasionally from a small sachet available from the manufacturer. The lips run directly on the shaft, which needs to be smooth and damage free. Volvo seals are reliable and long-lasting, a life of 10 years being common.
The seal is not vented in any way. On immersing the seal, whether at first launch or after drying on a tide, air will accumulate in the bearing. Running the shaft in this condition will cause a squealing noise and rapid wear. It is necessary to ‘burp’ the seal, compressing it in the lips area by hand to allow air to be dispelled. A small amount of water should be allowed into the boat to ensure that no air remains.

A shaft seal would normally be replaced with the boat on the hard. It is possible to change a Volvo seal (or most other types) afloat, as this video shows. Not advisable without some experience of doing it in easier circumstances.

The video is private and doesn't run.

Mt question is, what does 'On immersing the seal' mean? Is it bad punctuation and should it read: On immersing, the seal' as surely the seal does not run immersed.
The boat is currently in the water with someone keeping an eye on it and the pump running until she is moved to a drying out berth very soon hopefully.
Mike
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Mine is below the waterline so runs immersed.
 
Jissel sits in Portsmouth mud for a couple of hours each tide, so comments about abrasive mud made me wonder about the Radice and clones.

Many seals use a takeoff from the engine exhaust got lubrication, while the Radice seems to rely on water coming up the stern tube. If, rather than just using the vent pipe to allow air out, I were to attach it to the pipe that runs from the thermostat to the exhaust elbow (raw water cooled VP2003), would that provide cleaner water and help blow the mud out of the seal, or would the temperature of the water be too high? If so, for the relatively low flow rate, I could use a couple of feet of copper fuel pipe. Am I right in thinking that would cool the water enough?
 
It is more normal to T into the cold supply from the seawater pump to the engine, although this is not normally required for slower craft. Is the pipe from the thermostat to the elbow the only water that passes into the elbow? If so, this water is needed to cool the exhaust hose.
 
The hose in question is a bypass from the thermostat directly to the elbow. I think it would have provided hot water for a calorifier on the boat the engine came from; I'm pretty sure there's more water comes up through the head into the elbow.

Jissel is definitely a slower craft, and the Radice seal talks about the water pipe being a vent intended to avoid the need for burping. I'm just wondering whether the seal would last longer if mud was blown out of the stern tube from the top rather than being carried up by the water. as it rises into the seal.
 
Right, I know the hose you mean. Once the thermostat opens the water will be pretty warm 65C plus. Not sure what this might do to the seal. Is there a big history of wear by mud on drying moorings? Doesn't seem like a big risk to me as there is no driving force to carry mud up the stern tube.
 
I think that's what I wanted to hear! I have a tendency to overthink things, which doesn't always end well.

Radice it is. I'll have to wait for lift out to find out which one. The Orbitrrade from ASAP looks good too, but the one for the smaller shaft doesn't appear to have a vent pipe - or is it just a poor illustration?
 
Apparenlty the vent pipes on some deep water seals are required for high-speed operation (above c.14Kts) in order to ensure a flow of water into the bearing - at speeds above this I gather water may be drawn out of the shaft by the slipstream and air drawn into the bearing via the seal.
At lower speeds a stub tube vented to the atmosphere higher than (heeling) waterline is sufficient to 'burp' air out of the seal rather then a positive feed.
 
I fitted the radice type seal from aASAP. I have a clear tube as the vent so I can see the water level.
When going in reverse if I go too fast the water spits out of the tube . I have a Kiwiprop which is very good in reverse.
I talked to ASAP and I put a plug in the top of the tube which has cured the problem. I previously had a Volvo seal on another boat and when the water is in the seal it is effectively sealed so no difference to sealing the vent pipe.
I chose the vented seal as I can’t get to the seal itself to burp it (Volvo seal) as it is partly under the battery boxes.
It has performed faultlessly for 2 seasons and is also easier to grease than the Volvo one.
 
rotrax said:
The guy who wired up my plotter and radar on a previous boat was debating changing his Volvo stuffing box as he had been advised that they had a five year life.

His was drip free and working perfectly at 14 years since he fitted it.

Many other recorded instances of long life and conversly, very few stories of drastic failure.
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I have two opinions on this depending on my mood
a) as they are relatively cheap (I believe > £80) why not replace every 5 yrs as recommended by the manufacturer
b) if it ain't broke, don't fix it
 
ghostlymoron said:
I have two opinions on this depending on my mood
a) as they are relatively cheap (I believe > £80) why not replace every 5 yrs as recommended by the manufacturer
b) if it ain't broke, don't fix it
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c) Really should have done so and so, but it's probably be last another season before it fails completely

RivalRedwing said:
and, if i may hazard a guess, a) is the point of view at the end of the season whilst b) comes into play in the month before launching ;-)
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Sounds like my usual project plan for the winter.:)

The road to hell...
 
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