stern gland packing

[petersto]

Over the winter I renewed my cutlass bearing, shaft, rubber gaiter and repacked my stern gland. All seems to be fine, vibration free and much quieter. However the stern gland is getting hot. What I would like advice on is:
a. is this normal
b. if so for how long
c. if not does it mean repacking
The old packing was accurately measured for the new replacement. Also I have pumped grease at the start and each time I have taken her out.

 

[Guest]

To me as a non-engineer ... sounds as if its too tight.And possibly no water getting to it from outside ?

As I understand it - the occasional drip is preferable - it shows that cooling water is getting through ..... as well as to ease lubrication along with the grease.

 

[Salty John]

If the stuffing box is hot it is probably overtight. When I had this problem I just backed the nut off and thereafter the box ran slightly warm but not hot. There should be a drop of water every few seconds when the shaft is rotating.

 

[Guest]

If your assembly has a rubber tube between the fixed part and the packing gland then beware of tightening the packing too much. The frictional forces put a lot of strain on the rubber tube. We met a yacht that came down from Alaska and just after leaving, the tube tore in half.

The owner ended up diving under water INSIDE his boat to cut off the torn end and slide the packing gland down onto what was left of the tube. He said it was cold!

Also there has been a change in the type of packings that are sold for boats. Most are heavily impregnated with PTFE. This substance, although nicely slippy, has no real compression ability. Therefore there is no adjustment difference between too tight and too loose. It also has a tendency to creep. I have gone back to a non-PTFE packing and it is working well with the grease. Originally it was just flax. But there are aramide versions with only slight amounts of PTFE.

Does the grease get injected into the centre of the packings? Is there a spacer located at that point to allow the grease to get all the way around. On a non-greased bearing (water cutlass type) there should be a packing to stop the grease going out to sea.