How to spec the shaft log packing?

It looks like I need to service my shaft log packing. I have been needing to tighten the shaft logs more and more frequently, and now the difference between too tight and too loose is about 1/8 of a turn on the nuts so I think my packing is fully compressed.

This will be my first opportunity to try this so I am wondering what I measure to find out what size packing to order. I think it will be the difference between the drive shaft diameter and the inside diameter of the shaft log tube. Is this correct, or do I order material a little larger or smaller to allow for the compression?

Here is a photo of the shaft log (in case I am using the wrong terminology.)
This photo is from my pre-purchase survey, the nuts are now about 1/2" further down the studs.

The engines are Lehman 120, and the transmissions are Velvet Drives.


Thanks, once again, in advance for your help.

Frank

Yes, the packing size: 3/8", 1/2" or ? is the difference you noted. If you use Gore packing you will never have to replace it again and once seated will require little or no adjustments over time.

David

Measure dia of shaft. Measure outside dia of the part compressed by the nuts. Subtract and divide by two. If in doubt, buy both of the closest sizes and return the one not used.

I just loosen the bronze part that pushes on the flax and find a drill bit that fits the packing space.

Depending where you purchase a modern material like Duramax it may be cut to length for your order.

You will usually have to get too much as unless on land you cant remove and count the rings of packing used.

I replaced the packing today. On the port shaft I pulled 3 of the 4 layers, leaving the last one and adding 3 new layers of new material. On the Starboard side the 4th layer came out with the 3rd layer and I had a bit of a fountain going on. I had pre-cut the replacement pieces so I was able to put them in quickly. After the first one the water was mostly stopped, and by the 3rd, it had stopped.

The material was pretty tight so even without any tension on the nuts there was no drips. I took the boat out for a run, easing along at 1000 rpm. Initially the bronze casting got up to a little over 100 degrees F. Over the span of 45 minutes the temps dropped to the low 80s. Normally they are around 60, so they are still a little bit elevated, and they are still not dripping at all. I think as the material takes shape to the shaft logs I will eventually get some drips, and cooler temps. At the end of my run the nuts were still completely slack. I'll take her out again tomorrow for a longer run monitoring the temps and checking for the dripping to start.

If using any packing with teflon, and probably graphite, drips are a thing of the past.

If you can see moisture at the front of the rings, you are good to go as long as it is warm and not hot.

I have run many shafts this way with temps in the 100 degree range ....which is fine.

If you see a pile of goo that keeps reforming under the packing after a couple of runs, then backing off a tad is probably warranted.

OK, good to know. I bought the white stuff at West Marine. So that would be great if I end up with a dry bilge.

Thanks for the info!

Good choise , re the white packing more than likely is a Teflon based packing, by the way be careful if are going use Graphite impregnated packing in your marine underwater applications, these Graphite packing's are generally designed for industrial applications where dissimilar metals and sea water are not combined,

Some marine supply companies have come up with Minor Graphite particles held in suspension and as long as protected by the shaft zinc should present no problems but again be aware of true Graphite packing can cause an issue due to the fact that Graphite is near on the most noble material found on the Galvanic scale just to note the ABYC recommendations as Quote:
ABYC Standards:
"6.7.4 Graphite impregnated packing material shall not be used because of the possibility of galvanic incompatibility with the shaft material." End Quote,
CAVEAT: Also note my ABYC manual is way out of date so perhaps there advice has changed! Where as my Lloyd's Register manual is up to date and basically states the same risk's involved with Graphite packing's

Today how ever with the use of more modern shaft materials moving away from the more conventional 316/316L it's not the issue it used to be, how ever I for one would still recommend yearly checks for corrosion.

Cheers Steve

Steve is correct, graphite packing is not for boats. Also, your bonding strap is showing a lot of corrosion, I would service that too.

Xsbank said:

Steve is correct, graphite packing is not for boats. Also, your bonding strap is showing a lot of corrosion, I would service that too.

Click to expand...

Yes, that is an excellent observation. Now that I (hopefully) have the shaft log water flow under control I will clean them and get those grounds replaced.

Thanks for pointing that out.

Is a wire brush the best way to clean the corrosion off the shaft logs?

Dont use a steel wire brush, USE brass brush or SS , there are various cleaning compounds you can use as well (if being careful)

Have no idea what Duramax is made from , only know it works , and is expensive.

1. Duramax Shaft Sealing Systems: Ultra-X High-Performance Packing
   
   www.[B]duramax[/B]marine.com/shaft-ultrax.htm
   
   Ultra-X is a high performance, non-asbestos, compression packing that is engineered specifically for the marine industry. Its excellent lubricity and high thermal ...
   
   

I wanted to switch to Duramax last time I changed packing, but none of our marine suppliers stocked it or knew anything about it. To bad I hear rave reviews from those who have made the switch.

"Duramax® Ultra-X® is a braided hydrophobic fiber packing. Because of its composition and design it lasts more than 5X longer and outperforms all flax and PTFE packings in marine stern tube, rudder and bulkhead applications. Duramax Marine® uses unique patented manufacturing technology to encapsulate graphite particles and impregnate specialized lubricants into expanded PTFE strands. It greatly outperforms competitors’ packing that loosely blends graphite particles between the strands during the braiding process."

The hassles with old style flax packing , and the newer teflon is the materials hardness.

As metal flakes off the shaft it is stuck in the packing where it wears at the shaft.

Thats how the groves in the shaft under the packing are created.

The claim is the Duramacx is so soft that metal flakes sink rather than hold up.

It is also soft enough to fill a scored shaft (within reason) so it can be used again.

I have about 3 hours running time on the new packing. (Name and link below)

Before I changed the packing I was getting readings of 65 to 70 degrees on the shaft log housing. Now I get 75 to 80 degrees at 1000 to 1500 rpm, and the port side goes to 170 degrees at 2300 rpm. The starboard side stabilized at 85 degrees at 2300 rpm.
The adjustable flange is loose and not applying pressure to the packing (while still in contact with the packing) but I am not getting any drips on either shaft.

Any ideas about what is going on? The packing material was the correct size, I put it in by hand, but it was loose on the top halves of both shafts, and very tight on the bottom halves of both shafts.

-------------------

WESTERN PACIFIC TRADING - PTFE Flax Shaft Packing

from West Marine:
https://www.westmarine.com/buy/west...MI2ZLDi-nt1gIVDHp-Ch0mSQ8aEAQYBCABEgJgafD_BwE

f508 said:

Before I changed the packing I was getting readings of 65 to 70 degrees on the shaft log housing. Now I get 75 to 80 degrees at 1000 to 1500 rpm, and the port side goes to 170 degrees at 2300 rpm. The starboard side stabilized at 85 degrees at 2300 rpm.
The adjustable flange is loose and not applying pressure to the packing (while still in contact with the packing) but I am not getting any drips on either shaft.

Any ideas about what is going on? The packing material was the correct size, I put it in by hand, but it was loose on the top halves of both shafts, and very tight on the bottom halves of both shafts.

Click to expand...

Really hard to diagnose, without seeing it in person. I'm guessing, but I would say there is too much packing material in the nut. Maybe recheck the fit as it shouldn't be running hot. Maybe it's in your technique for cutting and fitting the rings?

Before I cut the packing rings, I wrap one loop around the shaft and (with a small hammer) tap the packing material gently all the way around the loop and it will form to the shaft. (Don't tap so hard that it loosens the material braiding) Then I cut the packing just short of a complete circle (about a knife blade thickness between the ends). Then slide the packing nut over the ring. If the ring doesn't pass into the nut, tap around the packing ring again until it does (stay away from the cut ends with the hammer though.) You may have to re-cut the ends again if they're too tight. Do that with each ring. Some people bevel the ends at an angles. I don't and have had good success.

I cut the packing so that it fit around the shaft with about 1/16' clearance at the end of the packing around the shaft, and I placed it on the shaft in the same orientation as it is here, so that the top surface that you see in the photo is parallel to the shaft surface, and the bottom surface, resting on the tape would be in contact with the shaft.