Burping a Stuffing Box

[glcalahan]

Hello,

I just saw the thread about stuffing box drip and I am dealing a slight variation. I am doing a total rebuild of a '72 Pearson and the boat was on the hill for 19 months while I replaced a new prop, shaft, cutless and packing gland. I also pulled the engine (Yanmar 2GM20f) and rebuilt and replaced. When I packed the packing nut I used 3 strans of Teflon packing and it was very snug on the 7/8" shaft. After I aligned the engine the boat was splashed. I have no was weeping/dripping w/o tightening the nut. I have 25 hrs on Yanmar and no water still. Now I believe I see reminents of black bits of the packing. Someone asked me if I Burped.....purged the air. Speechless....I said no. BUT it makes sense now that I think about it. Anyone ever hear of airlock in stern tube to packing gland????

Now I am concerned that I scorched the shaft and also am going to change out packing flax.

Comments???

[a64pilot]

Never heard of having to burp a stuffing box, only dripless ones.
Reason is of course if it won’t hold water back, it’s got no hope of being air tight.

I had the Teflon packing installed in mine, then when I took the boat out, it got pretty hot and didn’t drip a drop, so I loosened it. It still doesn’t drip, but runs cool and it’s been three years since.
How hot does your run? If it never got hot, then I don’t think it hurt anything.

[glcalahan]

Originally Posted by a64pilot

Never heard of having to burp a stuffing box, only dripless ones.
Reason is of course if it won’t hold water back, it’s got no hope of being air tight.

I had the Teflon packing installed in mine, then when I took the boat out, it got pretty hot and didn’t drip a drop, so I loosened it. It still doesn’t drip, but runs cool and it’s been three years since.
How hot does your run? If it never got hot, then I don’t think it hurt anything.

Thanks.....I forgot to mention that I used an infrared gun and temp was ....I think, 110-120°.

[a64pilot]

Originally Posted by glcalahan

Thanks.....I forgot to mention that I used an infrared gun and temp was ....I think, 110-120°.

Assuming warm water, I’d say that is fine.
Rule I was always taught if it’s not uncomfortable to hold for an extended period, then it’s fine. That was for the old style waxed flax though, maybe Teflon ought to run cooler? I don’t have a number for that though.

[hzcruiser]

Originally Posted by glcalahan

Thanks.....I forgot to mention that I used an infrared gun and temp was ....I think, 110-120°.

120 deg C is not a problem at all. And yes, a stuffing box cannot be burped, it has to drip water slowy while the shaft is spinning. If it's not dripping I would either loosen the clamp or put a temp sensor on the tube and set an alarm if it ever gets too hot.


My old dripless needed to be burped which, at the time I didn't even know. In hindsight I do remember the shipwright burping it at previous splashings, but not this time.

Then, after one hour of motoring on a windless day the rubber caught fire and it took about half an hour, a fire extinguisher and many buckets of water to cool the tube and shaft down again.
The new dripless is force fed with water from the raw water pump and also doesn't need the burping anymore.

[ArmySailor]

Wait...120 degrees "C". ?! Dats too hot

[ArmySailor]

Originally Posted by ArmySailor

Wait...120 degrees "C". ?! Dats too hot

Mine runs 80F, I use a laser temp gun to check it sometimes. Cool to touch. BTW those temp guns are cheap and come in handy for things exactly like this

[David M]

It is why I prefer the dripless types with water injection from the raw water pump.
Temperature and dripping is never an issue.

[a64pilot]

Originally Posted by ArmySailor

Mine runs 80F, I use a laser temp gun to check it sometimes. Cool to touch. BTW those temp guns are cheap and come in handy for things exactly like this

What is the water temp? That’s about 5 degrees cooler than the water I usually am in

[saillr]

Originally Posted by David M

It is why I prefer the dripless types with water injection from the raw water pump.
Temperature and dripping is never an issue.

David. My humble suggestion is "You are Nuts"
With Teflon packing you have no drips, does not run hot if not packed too tight and has no carbon faces to wear out or water burps to worry about. I have had Teflon packing in my Island Packet 40 for 20 years. Never dripped, never got hot and i snugged it up once maybe an eighth of a turn about 5 years ago.
Anybody who thinks Dripless types with water injection are superior needs to take another look at Teflon.

[hzcruiser]

Originally Posted by saillr

David. My humble suggestion is "You are Nuts"
With Teflon packing you have no drips, does not run hot if not packed too tight and has no carbon faces to wear out or water burps to worry about. I have had Teflon packing in my Island Packet 40 for 20 years. Never dripped, never got hot and i snugged it up once maybe an eighth of a turn about 5 years ago.
Anybody who thinks Dripless types with water injection are superior needs to take another look at Teflon.

Not sure anyone insinuated one being superior to the other. In the old days, there was no teflon, just flax or hemp impregnated with wax. I would much prefer a maintenance free teflon packing to the dripless seals that need to be replaced every 5 years, but that's what came with the boat. I just bought a new one last week.. maybe I should've looked into a conversion?


And of course, 120 deg C is too hot for normal use but I doubt it caused any damage in this case.

[Capt. Ray]

[120 deg C is superheated steam hot. Do you mean deg F? That would make more sense.

PS about time the US caught up with last millennium.

QUOTE=hzcruiser;2894173]120 deg C is not a problem at all. And yes, a stuffing box cannot be burped, it has to drip water slowy while the shaft is spinning. If it's not dripping I would either loosen the clamp or put a temp sensor on the tube and set an alarm if it ever gets too hot.


My old dripless needed to be burped which, at the time I didn't even know. In hindsight I do remember the shipwright burping it at previous splashings, but not this time.

Then, after one hour of motoring on a windless day the rubber caught fire and it took about half an hour, a fire extinguisher and many buckets of water to cool the tube and shaft down again.
The new dripless is force fed with water from the raw water pump and also doesn't need the burping anymore.[/QUOTE]