Stern Gland Maintenance again

[MedMan]

I was rather hoping that someone would have answered affinite's question on Stern Gland Maintenance in a previous thread but either no-one noticed it or all the experts have swanned off to the Lounge. Perhaps I could have a try with my own question on the subject:

Some 12 years ago I had the packing replaced in my Stern Gland - three rings of some form of graphite-coated 'rope' made for the job. A few months after the job was done I nipped up the gland less than quarter of a turn to stop a very slow drip but since then I have done nothing other than give the greaser half a turn every couple of hours whenever the engine is running. The shaft runs smoothly and there is no sign of a leak. To clarify that a little: if the engine has been running for several hours there is evidence of a tiny splash of water below the gland, but if I stick my head down the hatch determined to see an actual drip form, I never, ever see one.

And so to my question: Is this a case of 'if it ain't bust, don't fix it' or should I be stripping the gland down to see what is going on inside?

 

[l'escargot]

Sounds like it is perfectly set up to me - I would leave it alone.

 

[muchy_]

So would I.
Leave it alone that is. Sounds ok to me.

 

[eyehavit]

That is a long time for what is essentially a wearing part. If there is a bearing behind the stuffing box, after 12 years I would check for wear. It is better to plan mainainence than unexpectedly have it thrust upon.

 

[mireland]

I agree with eyehavit. Although there is clearly no urgency over this my own experience is that you will not be happy until you know for sure what is going on. Serious problems and tragedies arrise from chains of apparently minor decisions so plan to do the job when it fits in with your schedule and enjoy your sailing!

 

[trev]

Its considered by some, more learned than I, to be a good thing to have a little bit of a drip from the gland - it means its not heating up and drying out.

 

[macd]

Quite agree. The gland is water-cooled: it's supposed to drip. One drip per minute seems to be the usual rule of thumb

 

[l'escargot]

I think the dripping principle is more to demonstrate that the packing isn't too tight and causing excess friction - 1 drip a minute isn't going to disapate much heat or have any significant cooling effect, it would evaporate immediately with even a moderate heat.

 

[MedMan]

Thanks for your thoughts. Next time the boat is ashore I'll keep a look out for a fellow yachtie with 2 metre long arms and two elbows on each one. He (or she) might just be able to reach the gland for me.

 

[brianhumber]

12 years is a long time, but wear will depend on amount of hours run, speed of shaft and tightness of packing.

These shaft seals are cooled by allowing a drip per minute if running as a pump continously or the packing will get hot and rip the shaft leading to scoring and ridges.

On a small boat unless its high powered and running at say 5,000 revs you can get away without drips as long as the gland nuts are not done up hard but just enough to stop dripping, sounds as if this was done 12 years ago, the impregnated lubricant will then form a seal to stop any drips and the slow speed means it never gets hot enough to run out and start dripping again.

I am more concerned after 12 years that you used graphite. Graphite and stainless steel are not good bedmates in the galvanic corrosion tables and you could find some pitting has occured in side the gland on the shaft especially if not in constant use.

 

[MedMan]

I'm not 100% sure about the graphite. The job was done by a competent boatyard and I think that's what they said at the time, but I could be wrong.

 

[baldy]

Just reading the threads on this, all interesting stuff. I don't want to start this all off again but my stern gland is dripping at 6-8 drips per minute and it was professionally re packed last May. A problem? or should I just tighten the Gland?

 

[l'escargot]

Tightening the gland half a turn should do it.

 

[kds]

But surely, there is NO bearing behind the stuffing box - it is at the other end of the shaft log or on a bracket. That is why the stuffing box is on the end of a piece of hose, which allows for the fact that there may be some misalignment between outer bearing and uv joint and gearbox ?
Ken