Leaky stern gland… with an unusual twist.

[alexincornwall]

Since we took ownership of our Bowman 40 last year, we’ve always had a minor stern gland leak. The packing is in excellent condition, the gland nut suitably adjusted just before we went back in a few weeks ago, and it’s always greased as required. The leak appears whether the engine is on or not and I’ve never been able to visibly observe any drips. Usually we pick up around half a pint every few weeks so hardly keeping me awake at night but here’s what I can’t get my head around; the water that I periodically sponge out tastes completely fresh. Not a hint of salt in the water.

The moulding of the shaft and stern gland hull matrix is completely independent of the rest of the bilge and there are no fresh water lines running anywhere within this section of the boat. I cannot conceive how fresh water could end up in this compartment regardless of where it originated.

If it helps to know, dust could generally be blown around the other bilge compartments.

Any ideas why the water doesn’t appear to have come from below the waterline? I'm half expecting to feel like an idiot but looking forward to being enlightened on this.

 

[Refueler]

If you have a traditional stern gland with packing and a nut with greaser - then you should actually have a slow drip when shaft is running. You can give a turn on the greaser when finished with engine to stop the drip and accumulation of water ... but only enough to stop the drip... not more. Its important to have the drip when running ...

As to FW taste - are you sure its not condensation collecting ... as you say its a small amount over quite a period.

I have a couple of small lockers that do exactly same ... they seem to be the collectors of all condensation and it can amount to quite a volume over time.

 

[Poignard]

If it is not salt water it can't be a sterngland leak (unless you sail in rivers or lakes)

Might it be rain?

 

[alexincornwall]

If you have a traditional stern gland with packing and a nut with greaser - then you should actually have a slow drip when shaft is running. You can give a turn on the greaser when finished with engine to stop the drip and accumulation of water ... but only enough to stop the drip... not more. Its important to have the drip when running ...

As to FW taste - are you sure its not condensation collecting ... as you say its a small amount over quite a period.

I have a couple of small lockers that do exactly same ... they seem to be the collectors of all condensation and it can amount to quite a volume over time.

On the drip, I agree although I've never felt any heat build up in the shaft.

I don't think it would be condensation as this is the only part of the boat where there is evidence of water.

 

[ctva]

Some strategicly placed paper towels in the bilge might indicate where it is running from.

 

[alexincornwall]

If it is not salt water it can't be a sterngland leak (unless you sail in rivers or lakes)

Might it be rain?

I agree, it shouldn't be possible. What I should have added to the original post is that there was no build up in this area when the boat was on the hard, so surely it must be a leak. This compartment is sealed (excepting the stern gland of course) so I can't see how rain could get in there. Any rain etc. that gets into the boat through other means - anchor locker etc, runs into the main bilge.

 

[Refueler]

On the drip, I agree although I've never felt any heat build up in the shaft.

I don't think it would be condensation as this is the only part of the boat where there is evidence of water.

I hyave no evidence elsewhere also ... but because those two small lockers are bare GRP and below waterline ... condensation is the only answer for why water collects in mine.
They sit either side of my engine basically under the 1/4 berths that run under the cockpit benches.

 

[MoodySabre]

I agree, it shouldn't be possible. What I should have added to the original post is that there was no build up in this area when the boat was on the hard, so surely it must be a leak. This compartment is sealed (excepting the stern gland of course) so I can't see how rain could get in there. Any rain etc. that gets into the boat through other means - anchor locker etc, runs into the main bilge.

Rain is sneakier than that. The boat will have sat at a different pitch/tilt on the hard compared to in the water. Paper or talc in the bilges should track the direction from which it comes. Or it could be a drip from the calorifier PRV which can often be cleared by clicking it round.

 

[Praxinoscope]

I have a similar thing on my Sadler 25, and all through the season I was convinced that the stern gland (old style stuffing) was leaking, so on lift out dried out the bilges and started to think about doing my 'Houdini' act in the cockpit locker to access the gland, but....more water in the bilge, can't be the stern gland so now think it is the lbolt down 'hatch' In the cockpit floor, that must have been added when the engine was replaced by the previous owner. Sounds as if the OP has a similar problem from somewhere above the waterline.

 

[doug748]

You could try splitting a plastic milk bottle along it's length and putting it under the gland - just to be double dog certain it was not the culprit.

 

[Caladh]

Is there a hidden fridge drain or calorifier drain that could be causing the fresh water?

 

[Tamar]

Could it be rain water? I also have around a pint of fresh water in my bilge's after around a month, I can't see any obvious leaks so I'm putting it down to condensation.

 

[alexincornwall]

Is there a hidden fridge drain or calorifier drain that could be causing the fresh water?

No, they both drain to the main bilge.

 

[Spirit (of Glenans)]

I agree, it shouldn't be possible. What I should have added to the original post is that there was no build up in this area when the boat was on the hard, so surely it must be a leak. This compartment is sealed (excepting the stern gland of course) so I can't see how rain could get in there. Any rain etc. that gets into the boat through other means - anchor locker etc, runs into the main bilge.

While in the water the hull will be much colder than when on the hard, leading to possible condensation.
Leaking deck fittings allow rain to enter. Sometimes this can travel quite a long way, below decks before it becomes evident. Blue hand-towel paper is an excellent medium for tracking the path of mysterious minor water ingress.

 

[Refueler]

My preferred tracker for water is coloured talc ... ....

I have one mysterious 'drip' over my stbd fwd bunk ... for weeks nothing even in rain etc. ... then suddenly there will be a small wet patch on the bunk and a drip from the deckhead. Never been able to find out from where.

I ended up buying Captain ??? stuff to dribble around window frames / ports / fittings etc. - it basically wicks in wherever water goes .. and ZAP it seals it !! Not cheap - but lot cheaper than replacing frames / seals !

 

[Old Bumbulum]

If the boat is in salt water and the leakage is fresh than it cannot be from the stern gland.
The only alternative is that fresh water is accumulating there.
There are omly a limited number of ways that can happen.

Condensation.
Leakage from the fresh water system.
Rain ingress.

I can thnk of no others at all.

If the fresh water plumbing offers the remotest possibility of access to the area by spraying then you can eliminate the fresh water system by placing a temporary polythene sheet barrier between it and the area where the water accumulates. (if it's all the other side of a bulkhead or barrier you can probably eliminate this as the cause.)

Then you need to find how else the water arrives there.

There are only two possibilities. Either;
1) it drips directly from above
or 2) it runs down the structures/hull around the 'reservoir'.

So cover the reservoir with a tray of some sort. (baking tray, washing-up bowl) That'll tell you if it's direct drippage or not.

Simultaneously you could use watercolour or poster paint (water soluble) to paint a line all around the 'reservoir' which will indicate from which direction any run-down is occurring.

That will tell you whether you need to be looking for a drip from above (from an area the size of the tray you've used which narrows the area down enormously, and could then be refined by narrowing the same technique) or a dribble from a specific position defined by the washed away paint which probably more likely. From there the same technique will eventually pinpoint it. Water soluble paint has the advantage that it tells it's tale long after any leak has passed and dried up.

Unless your freshwater tank is sweating through the GRP there can't be any other possibilities, can there?

 

[LittleSister]

Rain is sneakier than that.

+1

There are omly a limited number of ways that can happen.

Condensation.
Leakage from the fresh water system.
Rain ingress.

I can thnk of no others at all.

Aren't you forgetting boat gremlins?

Schroedinger may have an explanation.

 

[Homer J]

May I suggest that you look at the water pump? it may not be the stern gland at all but a small drip from the impeller seal - I had the same thing.

 

[Homer J]

Having just reviewed your original message re engine off - could it be from the rudder bearing?

 

[tjbrace]

I have a similar problem, though I haven’t tasted the water. I think the leak is from the emergency tiller screw down ‘hatch’ situated on the hump of the stern seat. It has a seal but I don’t think it’s effective.