If you clicked on this picture to enlarge it you can see the black goo residue on the shaft caused by the "dripless" packing that was clogging my stuffing box. All traditional stuffing boxes require water for lubrication and this "dripless" stuff totally plugged the area between the shaft and the male end of the of the stuffing box as seen in the picture.


Even with the female nut totally removed, in the water, I was getting, at best, 4 drips per minute with the nut off! Please be cautious using this stuff! My stuffing box actually got so hot, from the lack of water lubrication, that it started to smell and I burned my fingers, enough to blister them, when checking on it.


Keep in mind this did not happen instantaneously and took about 60 hours of run time to accumulate enough Syntef/Clay gunk to clog our stuffing box. It ran at what I thought were normal temps during and after break in as I measured it with an infrared thermometer. I now know that "spot" temp checks do not tell the whole story. Temp spikes and excessive heat are likely what caused this stuff to clog my shaft log over time. In my opinion this stuff is not suitable for a "tight" shaft log where you don't have sufficient clearance between the shaft and the male end of the stuffing box.


I highly suspect that due to the "dripless" nature of this packing that air became trapped in the shaft log. This used to happen frequently with PSS seals before they went to vented or plumbed models that allowed any trapped air to escape. With entrapped air inside the shaft log the packing would have no water lubrication and could begin to melt and clog the shaft log making it worse, as I suspect happened here.


How does air get in there? Docking or anchoring with quick blasts of reverse will send cavitation air bubbles up into the shaft log. If the shaft log is totally sealed or "dripless" the air accumulates until it causes no lubrication and eventually damage. There is a reason traditional style stuffing boxes are meant to drip. These newer packings should be considered "drips less" not "dripless". Beyond entrapped air stagnant water in the shaft log can cause crevice corrosion of a prop shaft as you'll see below.