This photo shows three rings installed. This nut fits three, some don't and it's not a huge deal if one does not fit more than two.
My personal preference is for four full thread peaks of engagement between the female nut and male stuffing box threads. This is four thread peaks with three rings installed and seated.
Old Teflon RIngs & Syntef Shown With GTU Rings
Here are two of the new GTU rings and the old stuff. Note that there is some fraying even though I tried to minimize it. I have discovered that Western Pacific Tradings GTU frays more than Gore GFO or Duramx Ultra-X. GFO and Ultra-X barely fray at all.
Perhaps, to prevent fraying with GTU, you could heat up a little wax in a bowl and as soon as you cut the ring dip the ends in the wax like whipping a line. There is actually a fair amount man-handling, of the rings, between the time when they are cut and inserted and some measure of fray prevention should be attempted when using Western Pacific Trading GTU or just use GFO or Ultra-X.
The product I used above for this article was Western Pacific Trading GTU from West Marine. Initially I thought it was the Gore GFO I had lying around but GFO has the words "GFO" written on the packing and after going through the photos carefully I could not find the silk screened GFO logo.
I had never had GFO fray but the GTU did. The photo to the left is Duramax Ultra-X which has a very similar construction and braid to Gore GFO. It does not fray when cut like GTU does. I would try to avoid the GTU packing sold at West Marine if you are concerned about the ends fraying.
Johnson Duramax Ultra-X can be purchased by the foot from Hamilton Maine and it cuts cleanly.
Duramax Ultra-X Cuts Cleanly
Here's an image of a finished 45 degree cut. This was cut from Duramax Ultra-X. It is important to keep in mind that these Gore style packings can dull a razor blade quickly so rotate in a new blade if the old one is cutting poorly. Razor blades are cheap.
Mark The Nut Where Your Seams Are
When doing this in a boat it is a very good idea to mark the exterior of the nut where each seam is so you can stagger them. Use a packing tool like I show below to compress them into the nut. Only when all rings are in the nut can you then tighten it.
Tightening the nut to seat the packing, especially with the newer more slippery packing braids, can move the seam and you'll now be blind as to where your seams are. Best to make yourself a seating tool.
New Packing Rings
This is the last step! In this picture I have two of the three rings wrapped around the shaft in a stepped and alternated order. You must be sure to offset the rings butt joints 1/3, 1/3, 1/3 for a three ring box or 1/2 & 1/2 or said another way 12 o'clock and 6 o'clock for a two ring box.
It's also perfectly fine to wrap one ring at a time and push the nut over it BUT WITHOUT TURNING IT until you get all three rings into the nut and staggered. It's best when using this method of "stuffing rings" to mark the outside of the nut with a Sharpie marker where the joints are and then when all rings are in the nut, and staggered, you can finally thread the nut onto the box.
I custom made my own tool for this & it has a similar thickness to the flax for "stuffing the nut" (see the "tool" below). I don't advise the use of a pick to stuff the flax into the nut as this can cause significant unlaying or twisting of the flax especially with GTU. When ever possible try to get at least three rings of packing in your stuffing box as most are designed for at least three. Some nuts can actually fit four & if so go for it but make sure you have enough threads to get a good hold for the female nut.
One more very important note is that you really need to use the correct size packing. Going one size to big can eventually wear a groove in the shaft and one size to small will never seal properly. Please use due diligence to determine the proper packing size for your particular stuffing box.
My Home Made Flax Insertion Tool
Many folks have asked me how I insert the flax rings into the female nut easily. Well, like anything dealing with boating, it's not always easy but can be done with a little Yankee ingenuity.
I decided that in order to keep my ring joints staggered, and to get them properly seated, I needed a new tool. I wanted a tool that was to be perfectly parallel with the prop shaft when inserting and seating the flax.
I also wanted to to seat the flax without causing any twisting and there were no commercially available tools, so I made one. Using a screw driver will not give you the correct angle to seat the flax properly and could potentially mess up the joints or put twists in the flax rings.
Flax Tool On Shaft
Making this tool took less than five minutes but can really save time and headaches. To build this device I decided to use a short piece of 1-1/4 inch PVC pipe with about 1/3 of it cut out so it would fit over my shaft.
I left just enough material so it could clip itself onto the shaft and stay in place without hand holding.
For this process I cut the 1-1/4 inch PVC pipe to 2-1/2 inches long. I then inserted this 2-1/2 inch piece into my bench vise and used a hack saw to make two more cuts. These cuts removed just enough of the 1-1/4 inch PVC to create the device.
You're probably wondering why I used 1 1/4 inch PVC if I had a 1 inch prop shaft? Well.. I used it because it's all I had on hand and I also own a heat gun so it was very easy to heat the PVC and wrap it around a piece of scrap 1 inch dodger tubing for a perfect heat formed fit. If you don't own a heat gun dropping PVC into boiling water will soften it enough to "mold" it..
Seating The Flax
This photo shows the female nut sliding over the "flax seating tool" and seating the flax. The tool works very well and unfortunately no one actually makes one?? Hey I bet West Marine could sell one for $50.00......Hmmmmm...
GFO, GTU & Ultra-X Warning
*WARNING: While I do like the graphite impregnated packings such as Duramax Ultra-X, Gore GFO or Western Pacific Tradings GTU they can be dangerous to underwater metals. I have used it on my own boat but inspected the Aqualoy 22 prop shaft yearly.
Graphite is one of the most noble metals on the galvanic scale and is basically at the top. As such anything in the drive train becomes anodic to the packing. Older "bronze" shafts, really more like a brass because they had high zinc content, can be damaged by these new high tech packings.
The damage shown in this photo happened in one season with intact prop shaft zincs. The shaft was in fine condition when packed and a year later this is what it looked like.
The packing used was Gore GFO a graphite impregnated packing. If you have a bronze shaft use extreme caution with graphite impregnated packing materials.
I don't tend to see these issues with Aqualoy 22 shafting but I have seen it with bronze and lower grades of stainless. Please use these packings CAREFULLY. If you choose them please do check on the shaft periodically.
It should be noted that ABYC P-6 specifically says this:
"6.7.4 Graphite impregnated packing material shall not be used because of the possibility of galvanic incompatibility with the shaft material."
That being said there are thousands of happy boaters who have had decent results with these packings. However, they should not be treated as a "set it and forget it" packing. If using these graphite impregnated products I would suggest checking the shaft at least yearly.
Here's the finished product after installing three new rings of GTU packing.
When initially installing the rings of packing LIGHTLY tighten the nut just until you start to feel some resistance then stop! DO NOT OVER TIGHTEN THE NUT EVER!! the final adjustment will be made after running the motor and shaft for a while.
Proper adjustment for GFO, GTU or Ultra-X is up to a few drops per minute when the shaft is spinning. You'll want it adjusted for nothing more than slightly different from the sea water temp, about a 15 - 20 degree differential, or slightly warmer to the touch. Measure these temps after the shaft has spun for a while.
Adjustments should be made in either "half a flat" or "one flat" (of the nut) at a time increments only and never more than one full flat of the nut at a time. W.L. Gore recommends not adjusting the stuffing box until you have run the boat in gear for about two hours of time. This allows the packing to take a set and break in.
When adjusting other types of flax the stuffing box should be relatively cool/warmish to luke warm, at most. With traditional flax packing it should drip and must drip while the shaft is spinning.
The cooler your stuffing box runs, the longer shaft life you'll have. With GFO they claim temps up to the 125-130F range are technically safe for the packing. In my opinion this generally means there is not enough cooling flow through the box. Any entrapped air, with normal temps this high, can cause a big spike in box temp. Aim for 15-20 degrees warmer than the ocean or lake temp but a little higher, with GFO, GTU or Ultra-X, should not "kill the deal".
Some boxes will even drip when the shaft is not spinning and this can be entirely normal depending on the condition of your shaft. Do not get stressed if you can not make it drip free at rest as not all shafts are in good enough condition for this to always be the case.
Please do not get in the habit of tightening the stuffing box when "leaving the boat". Natural flax packings are not elastic and do have a memory, in a sense, and they will not necessarily return to their uncompressed state. Doing this will severely shorten the life of your packing and it will start leaking continuously in short order.
I generally don't like rules-of-thumb for drip rates and really hesitated to even put one on here. My reason for this is that every shaft has differing levels of wear and thus the drip rates are usually different in every installation.
The best rule of thumb I've found over the years is the least amount of drips when the shaft is spinning but before the box develops any heat. Again, it's a drip to heat ratio and little to no heat is the most desirable. Traditional flax packing can drip as little as about 5-10 drops a minute if adjusted correctly, while running, and this drip rate allows lubrication of the shaft.
Do not make adjustments to the packing nut, with traditional flax, for at least 24 to 48 hours as the plant based flax packing will absorb moisture and swell. This swelling can cause overheating of the stuffing box, if it is adjusted to quickly after launch and the swelling has not been accounted for.
Premature tightening of traditional flax can result in potential problems. A good and safe practice is to adjust the packing by "half a flat" turns after two hours of use or until you have your drip to heat ration correct. You can actually use an infrared thermometer, often called a pyrometer, to make this adjustment process easier but usually your hand will suffice as a good gauge.
If you want a totally dry bilge then a dripless type gland such as a PSS or Las-Drop is the way to go. I've provided full installation instructions for that type of seal too in the gallery preceding this one.
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