SailNet Community banner
  • SailNet is a forum community dedicated to Sailing enthusiasts. Come join the discussion about sailing, modifications, classifieds, troubleshooting, repairs, reviews, maintenance, and more!

Cotton String Trick for Changing packing in stuffing box

2K views 6 replies 5 participants last post by  capta 
#1 ·
I saw a post on one of the boards, I think it was the Hunter Owners site that had a picture of cotton string that had been coated with some kind of grease or lube and wrapped around the propeller shaft after the packing nut had been removed to eliminate water ingress through the tube. My barnacle brain didn't think to bookmark the page and I can't seem to find it now.
I wanted to see what kind of lube that they were using, it looked like a really neat trick.
Anyone out there know anything about this?
 
#2 ·
This is bad idea except for a short term stop gap. When you add an additional ring of packing or cotton string coated with lube because the old packing ceases to seal properly the packing will only seal at that one point (i.e., the additional ring or the wad of string). When you tighten the packing nut all the pressure will be at that one point on the shaft and you will score the shaft. When you score the shaft you will be unable to achieve an effective seal. When your packing is worn out replace all of it so that the sealing pressure is distributed throughout the length of the stuffing box.
 
#3 ·
Water pump grease would do it but why carry that when you can carry a spare packing. Better yet just replace it, mine crumbled when I removed it, probably original on an almost 30 year old Boat. But in a pinch anything is better than nothing and they're water cooled.
 
#4 ·
The point of the greased cotton is to stop water ingress while you are changing the stuffing box packing while the boat is in the water. It's not to add to existing packing. Some people use an old bicycle inner tube for this same purpose and others simply let the bilge pump take care of the water ingress. I wish I could find the link that had the picture, thought it was a great idea and since it's time for me to change out the packing I thought I would give it a try. Just needed to know what they used to grease the cotton with.
 
#5 ·
Any good grease. Rub it well into the cotton string before putting it in as packing.

Definitely a temporary measure.

It actually depends on the condition of the other packing already in place as to the effect. If the old packing is still somewhat flexible then you'll compress it and get some sealing from it.

for some pumps and valves, the manuals will say to add a ring if the packing nut being tightened all the way doesn't cause the packing to adequately control leakage. Then you can continue operation until conditions allow for replacing the packing.
As some types of packing age they shrink.

Dealing with valve, pump and turbine packing was part of my job in the Navy.

There are definitely times you do whatever you need to do to keep stuff working until you can make the proper repairs.
 
#7 ·
Of course one could just wrap a piece of cloth around the exterior of the shaft log and let the water pressure hold it in place while changing the packing. Not all that much water comes in and there are no obstructions to changing the packing on the inside.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top