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Discussion Starter #1
I'm having some trouble with the stuffing box on the prop shaft of my sailboat and I was hoping someone on this forum may be able to shed some light on the problem. It started last fall, so we had the guys at the marina repack the stuffing box over the winter, but that did not fix the problem. Bascially, the stuffing box drips fine at rest and when the engine is in neutral. However, as we put the boat in gear and bring up the rpms, the dripping stops completely and the box gets hot. If we loosen the nut any more, then the box drips too much when the engine is not on. It's always been my experience that stuffing boxes drip more as the shaft spins faster, so do you have any idea why the box is acting in reverse?
Thanks for any input!
 

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Weird.... the only thing that occurs to me is that maybe whoever repacked the box 'spiraled' the packing in rather than using individual rings.. and perhaps in forward gear the friction of the shaft tightens the spiral, stopping the weepage.

Wondering if the the drip stops when running in reverse too?? If my (improbable) theory is correct the spiral would open up then...

The symptoms certainly are opposite the norm.
 

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Tartan 27' owner
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I'm with Faster(Ron) on this one.
The only way those symptoms makes sense is if a long piece of packing material was wound around the shaft (in a spiral) versus multiple individual rings (the way it is supposed to be done).
You also do not specify what kind of packing material was used which could make a difference.

I think the only thing to do at this point is open up the stuffing box again and pack it properly, per this link: https://secure2.pbase.com/mainecruising/stuffing_box

Welcome to SailNut by the way.
 

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The cuts on the individual rings should be offset around the shaft. The may also have not used the correct size packing. It should match the gap between the shaft and the gland.
 

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Discussion Starter #7
We think the stuffing box was packed correctly, and anyways, we had the same problem last season, that's why we got it repacked. I also suspect that if the prop shaft was worn or pitted or grooved the box would be leaking too MUCH. I think we might purchase one of those Infrared Thermometers and find out just how hot it really does get. Does anyone here have any idea of what an acceptable temperature range for a stuffing box is?
 

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Heat on the outside of the stuffing box indicates even more heat being generated by friction around the shaft, packing and stuffing box. Friction is to be avoided to protect your shaft, so no heat generated here is the ideal. Water dripping through when running helps maintain the temperature. Too hot to hold is way too hot; merely wam to the touch and easy to hold is probably acceptable.

I still think you may need to re-do the packing and I'll tell you why.

One of the last times I decided to change my packing material I mis-remembered and ordered 1/4" packing for the job (should have been 3/16", iirc). I installed the 1/4" packing but found that I had to force it into the "box". Bolted it up and motored off but the stuffing box was getting warm and the dripping wasn't right. Eventually I realized that the packing should not be crammed into the opening and decided to change out the 1/4" for 3/16" packing while on my mooring. Problem solved for me at least.

Do you know what kind of packing material was used in the stuffing box? Flax, GTU, Gore ... and/or the green putty?
 

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If the OP is getting into mechanics time and facing a haul out (more $), and there is a possibility of surface irregularities with the shaft, maybe it's time to consider replacing the stuffing box with a dripless type like PYI sells.
 

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Discussion Starter #11
I think Capt Len might be onto something. We're going to check out how much the engine moves on the mounts and then maybe look at the shaft.
 

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I'm having some trouble with the stuffing box on the prop shaft of my sailboat and I was hoping someone on this forum may be able to shed some light on the problem. It started last fall, so we had the guys at the marina repack the stuffing box over the winter, but that did not fix the problem. Bascially, the stuffing box drips fine at rest and when the engine is in neutral. However, as we put the boat in gear and bring up the rpms, the dripping stops completely and the box gets hot. If we loosen the nut any more, then the box drips too much when the engine is not on. It's always been my experience that stuffing boxes drip more as the shaft spins faster, so do you have any idea why the box is acting in reverse?
Thanks for any input!
Id strongly recommend to fully disassemble the stuffing box, remove and visually inspect the shafting ... for galling (severe pitting or other metallurgical or surface irregularities), etc., etc.

Another possibility is that there may be galling (unequal wear on the shafting) present that allows a 'biological growth' or mineral deposits to form in/on the irregularities which (locally and in 'spots') changes the 'effective or apparent' diameter when the shaft is rotating ... the heating thermally 'enlarges' the shaft and the thermally 'swells' the installed packing. Usually such galling, etc. condition will promote more leakage when the shaft is spinning; but, in this case the 'stack up' dimensional 'irregularities' may be dynamically closing up the needed clearances which provide 'weep' water that provides the needed cooling and thermal transfer of/to the shafting and the stuffing box.
For this particular situation and if there is FLAX packing installed, Id first: REALIGN THE ENGINE; then, severely over tighten the stuffing box, then severely open up / loosen the packing 'tightness' and 'run the hell' out the engine/shafting ignoring the excess leakage, as such 'may' polish up the shafting surface a bit, may 'reshape' any 'wrinkles' in the surface of the installed packing, and 'may' flush out any accumulated mineral deposits, etc. that may be 'in error'.
If that attempt doesn't correct the situation; then, a complete removal of packing, removal of the shaft for visual inspection is in order. If this is needed, consider to replace the flax packing with Gore-Tex (braided PTFE) packing which can be 'run tighter' in the stuffing box and with better frictional characteristics which will produce less heating when the shaft is rotating.

Another possibility which can cause aggressive stuffing box heating is that the packing isn't 'concentric' within the stuffing box and the shafting ... unequal dimensions of packing on 'each side' of the shafting (because someone used a hammer to install the cut packing rings), causing the shafting to be forced to 'bow' or bend when running ... and will/can soon cause adverse wear of the cut-less bearing and transmission output shaft bearing.
To test for improperly installed packing which is 'deflecting' the shaft sideways etc., disconnect the transmission to engine coupler - slide back the shaft towards the aft end of the boat for a wee amount (0,125 to 0,25 in.) and MEASURE to see if the shaft and its 'coupler' properly aligns with the coupler on the transmission. If the two half sections of the coupler do not exactly line up ... this can be the cause of the 'heating' ... the 'bowing' of the shaft is coming in strong (frictional) contact with the stuffing box packing.

Best practice when changing packing is to totally disassemble 'everything', remove and inspect the shafting (journal) surfaces for developed wear and developed surface irregularities where the packing and cut-less bearing 'ride', install new packing .... then, REALIGN THE ENGINE to insure NO 'side pressure' on the shafting due to improper dimensional packing reinstallation.

FWIW- ENGINE ALIGNMENT should be done religiously every ~500 hrs. and the engine mounts fully inspected for 'sagging/compression ... or the need for replacement' -- much cheaper than replacing transmission bearings.

SIMPLE SYNOPSIS:
1. Check engine alignment !!!!! Realign as required.
1a. OPEN up 'tightness' of packing (to flush out the packing) and ....
2. RUN THE HELL OUT OF THE ENGINE (with packing loose and packing freely 'leaking' ).
You may have to tighten up packing when not running the engine/boat.
2a. You may have to 'tighten down' followed by 'loosen up' then run engine ... several times.
3. If that doesn't solve the problem .... inspect the shaft surfaces (galling or excess wear) and for 'bent shaft'; change the packing - (to GFO); realign the engine
4. Lastly, if the packing was sloppily installed, it MAY compress and realign itself over a short period of time ... by running the hell out of the engine in gear; as, sometimes it takes a while for the packing to 'settle in' to its normal shape and proper clearances.
 
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