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Discussion Starter · #1 · (Edited)
I have a traditional bronze stuffing box on my boat with teflon-impregnated packing material. I adjust it several times a year to get the right trickle of water while underway. Occasionally I put a laboratory tissue underneath it before departing, since it enables me to see the desired wetness instantly when I check it with a flashlight. When the boat has sat for awhile, it is normal to see a little gray color on the tissue, which I always attributed to dried minerals from old seawater.

This weekend I noticed some tiny yellowish metal specs in the tissues. The first picture below was after a couple hours of motoring yesterday (first time out in 3 weeks). The usual gray crud includes some yellow specs that I suspect are bronze from the stuffing box:

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The second picture was after about 30 minutes of motoring today. The gray crud was not present, which I believe was because the stuffing box had not dried out overnight. But the metal specs are still apparent on the white tissue:

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A few additional details:
  • Prop, strut, cutlass bearing, shaft, stuffing box, and coupler were replaced in 2019. Engine alignment was professionally performed at that time.
  • The new shaft is Aquamet 22 stainless
  • I do not see any signs of misalignment. The cutlass bearing wear looked to me like it was even during the 2019 and 2020 winter haulouts.
  • I note no unusual vibration. Shaft rotates easily by hand when transmission is in neutral.
  • I did have significant vibration starting at 2300 RPM in July 2020, but hiring a diver to clean hard growth from the prop and shaft immediately eliminated the problem. After cleaning, no vibration was noticed all the way up to 3200 RPM full throttle.
  • I normally motor at 2200 RPM and under, and occasionally go to higher RPMs to test for vibrations that may indicate hard growth on the prop. This weekend I sensed a tiny amount of vibration when testing above 2500 RPM, but it was nothing anywhere close to what I had last year. Nevertheless, I might call the diver again to be safe.
  • I do get some dried mineral deposits around the shaft near the stuffing box, which I periodically clean with CLR or cleaning vinegar. These deposits can be very stubborn to remove, and I wonder whether they might be abrasive enough to grind at the adjacent bronze on the packing nut. However, I am concerned that the metal flakes could indicate potential metal-to-metal contact between the shaft and packing nut.
Can you guys suggest other possible causes? Is it likely to be an alignment problem? Can you suggest any other things I could try before calling out a mechanic to look at it?
 

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If the packing material is protecting the gland, one might think it could be the shaft corroding or abrading. Hope not, but all shafts warp over time.
 

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Good question, it sure looks like bronze somehow getting pulverized. Can you see any wear near where the shaft exits the fitting in the bronze?
 

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Hunter 34
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Possible the packing nut is worn larger because of old shaft, maybe the packing box hose is out of alignment, maybe need new packing or the existing packing is slightly off center, but it's anybody's guess and of courseit's a major operation to replace any of it any of it other than the packing. 🤔
 

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Western Branch Metals (shaft mfg) says ...
"The use of graphite-impregnated packing is not recommended because of the possibility of galvanic corrosion of the shaft material. FEP Fluorocarbon-impregnated asbestos braid, the fibers of which are impregnated with the plastic prior to braiding, is considered to be excellent for shaft seals. Wax-impregnated flax packing may be used."

Many packings advertised as "Teflon" contain graphite.
 

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Hunter 34
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Western Branch Metals (shaft mfg) says ...
"The use of graphite-impregnated packing is not recommended because of the possibility of galvanic corrosion of the shaft material. FEP Fluorocarbon-impregnated asbestos braid, the fibers of which are impregnated with the plastic prior to braiding, is considered to be excellent for shaft seals. Wax-impregnated flax packing may be used."

Many packings advertised as "Teflon" contain graphite.
I I must say this is one of the most profound things I've read on this labor day morning!
 
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Discussion Starter · #7 ·
Western Branch Metals (shaft mfg) says ...
"The use of graphite-impregnated packing is not recommended because of the possibility of galvanic corrosion of the shaft material. FEP Fluorocarbon-impregnated asbestos braid, the fibers of which are impregnated with the plastic prior to braiding, is considered to be excellent for shaft seals. Wax-impregnated flax packing may be used."

Many packings advertised as "Teflon" contain graphite.
I inspected the packing before it was installed. It definitely does not have graphite. It is yellowish white in color and is a combination of Kevlar and Teflon.

The diver is coming this week to clean the hull and running gear, then I'll get some close-up pics and slow motion video to further diagnose what may be going on. Interestingly, I just learned that the kevlar/teflon is supposed to be adjusted to drip 1 drop per three minutes (1/9 the rate of the normal 3 drops per minute), so I may have the compression on the packing too low. After the diver is done I'm going to tighten it up some more and see if that keeps the nut better centered on the shaft.

I only have 162 hours on the stuffing (and the shaft), so I don't think that stuffing is anywhere near worn out at this point. Running temperature of the stuffing box is always <10 degrees above the ambient water temperature.
 
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You didn't say your stuffing box is on a hose or straight mounted. Alignment is best determined with a feeler gauge.(done right) Appearance can be non effective. Pull the shaft coupling clear of the trans to see if it wants to be somewhere else. Ive seen shafts sprang several inches when allowed. Is it possible the stuffing nut has been cross threaded.? Careful alignment with feeler and patience. Are the engine mounts good.? If the shaft is visibly not centred on the nut maybe the shaft is being wooped over three points not in line. coupling centre, cutlass. and the body of the stuffing box.
 
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