stern gland packing is overheating

[walli]

Hello,

the stern gland (where the packing is) on my boat is getting very hot while in gear.

I have a boat with a conventional stern tube. On the propeller side there is a brass bearing with a lubrication groove on the inside. The motor side has a pusher with 3 layers of packing and a greaser. I had everything apart, since I did a complete refit of the boat. I put in a new propeller shaft, a new brass bearing on the propeller side and new packing. The greaser works (while on land grease came out of the propeller side) and has been refilled so often, so that the stern tube should be full by now.

I admit that I made a mistake and tightened the pusher to much before putting the boat in the water. After I noticed that it was getting much too hot, I untightened the pusher hoping this would reduce the friction. Nothing happened and no water is dripping out and the thing is still getting hot. Should it untighten itself when the pusher is opened or will the packing stay as is?

I am thinking of taking the whole new packing out at low tide and putting in 3 new layers, without over tightening the unit.

On the propeller side there is a cap with two screws holding the brass bearing in the stern tube. I put one ring of packing material between the cap and the brass bearing. Is this correct or should water be able to run in on the propeller side? I am not sure if the shaft is cooled by the little water coming in on the propeller side or only by the grease?

I did my best to align the engine with the shaft and have a flexible coupling. Could the heat come from a minimal misalignment? I would like to get this taken care of before the shaft gets ruined and finally get the boat moving again.

Can someone help me?

[churchward]

The stuffing may be so tight that it has stayed that way even though you have backed off the nuts or you have not backed it off enough. It may soon ware and loosen off that way but if it does not the only other answer will be to repack the bearing as you don't want the packing making a groove in the shaft.

 

I have not seen where a packing ring goes on at the prop end as these are usually on a tapper fit on the shaft.

 

The above assuming the alignment is good enough.

Edited September 15, 2015 by churchward

[Bee]

I doubt that misalignment is a problem. Can you turn the shaft by hand? or is it really tight? I think that the packing probably has stayed in the position it was when it was overtightened and the pusher may not even be contacting the packing now you have slackened it off, the water ingress could be because of this. If I were you I would just take the old stuff out and start again, tighten it till it contacts the packing and then when the tube is submerged just nip it up a bit more.

[walli]

Even when opening the pusher so that it is completely loose nothing happens – not even water comes in. I guess the best thing is to do it all over again and pack it loose first.

I also thought the packing on the prop side was unusual, but since there was a ring of packing under the cap I did the same. The question is, should some water come in through the prop bearing or not. If so I will take the one ring of packing out again. On the other side grease came out of the prop bearing so water should go in.

Yes I can turn the shaft by hand. It does not spin on by itself but it turns without using too much strength.

Thanks for your help, Douglas

Edited September 16, 2015 by walli

[nb Innisfree]

Try and pump grease through to the inside while the nuts are loose, this might unstick the packing.

Edited September 16, 2015 by nb Innisfree

[bizzard]

Sounds like you may have rammed some packing strands down between shaft and tube bearing if it doesn't free off with loosened gland nuts. If this is the case you will probably have to uncouple the shaft from the gearbox and shunt the shaft back and forth and round and round to free it. This happened to a boat here, the owner was forcing the boat along with the seizing up shaft and burnt the gearbox out. It took me about 3 hours to free the shaft as I described above.

[walli]

I will look for a good day when the tide is right, so I have enough daylight time and no water under me. I hope it does not take 3 hours.

Let you know what happens.

Douglas

[matty40s]

Sounds like the packing is too tight with not enough grease round it.If you take the packing out, you can hammer it flatter than the usual square profile, thus it should slide back in easier and then get some grease pumped round it before tightening.

[walli]

I changed the packing last week. The old packing came out easy and did not seem very tight. Before I put in the new packing I hammered it flat like Matty said. This was a great help. I greased everything well and did not tighten the pusher much, except for hand tight. After about 15 minutes of running in forward gear at a moderate speed the dam thing started getting hot again. While running the motor in gear I kept on turning the greaser as far as I could, but still it did not cool down. The only thing I can think of now is to untighten the pusher a bit more. I noticed that no water at all comes in. It seems the grease is sealing the bearings very well.

Must the packing always be in contact with grease and with water to keep cool?

After all the refit and motor problems I do find this very annoying and have no solution.

Thanks Douglas

Edited September 28, 2015 by walli

[ditchcrawler]

I changed the packing last week. The old packing came out easy and did not seem very tight. Before I put in the new packing I hammered it flat like Matty said. This was a great help. I greased everything well and did not tighten the pusher much, except for hand tight. After about 15 minutes of running in forward gear at a moderate speed the dam thing started getting hot again. While running the motor in gear I kept on turning the greaser as far as I could, but still it did not cool down. The only thing I can think of now is to untighten the pusher a bit more. I noticed that no water at all comes in. It seems the grease is sealing the bearings very well.

Must the packing always be in contact with grease and with water to keep cool?

After all the refit and motor problems I do find this very annoying and have no solution.

Thanks Douglas

If its still getting hot is the alignment spot on?

[walli]

If its still getting hot is the alignment spot on?

I tried my best to get the alignment spot on. I am not sure if I managed to get it exactly spot on since that has to do with 0,01 mm, but it is pretty close.

Even if not the stern gland with the packing is connected with a rubber, which gives a bit of flexibility. How would I get the alignment spot on with a flexible coupling.

[bizzard]

You shouldn't have to hammer packing flat if it's the correct size to get it in, If you did then it must have been a size too big which 'WILL' tighten it up. Was the shaft nice and free to turn when the old packing was removed? If it still overheats with the correct size packing fitted with the gland nuts done up 'just so' then either the shaft and or tube bearing is either badly worn or it's badly out of alignment with your gearbox output coupling or whatever flexible coupling you have.

[walli]

You shouldn't have to hammer packing flat if it's the correct size to get it in, If you did then it must have been a size too big which 'WILL' tighten it up. Was the shaft nice and free to turn when the old packing was removed? If it still overheats with the correct size packing fitted with the gland nuts done up 'just so' then either the shaft and or tube bearing is either badly worn or it's badly out of alignment with your gearbox output coupling or whatever flexible coupling you have.

Thanks, the packing is 6 x 6 mm and fits in. Since it is a hard place to work at I hammered the packing a bit flatter and greased it to make things easier. The shaft was perfectly smooth. It might have to do with the alignment. That means another few days in the motor room for me.

 

Once more to my question: should water drip out of the stern Gland?

Edited September 28, 2015 by walli

[bizzard]

Thanks, the packing is 6 x 6 mm and fits in. Since it is a hard place to work at I hammered the packing a bit flatter and greased it to make things easier. The shaft was perfectly smooth. It has to do with the alignment. That means another few days in the motor room for me.

 

Once more to my question: should water drip out of the stern Gland?

A few drips per minute is fine, it helps to keep things cool.

[ditchcrawler]

mine doesn't unless the prop gets fouled, but I have ptfe packing and a hydraulic drive with a thrust bearing and flexible coupling so no sideways force on the shaft at all, just a rotary motion.

[walli]

You shouldn't have to hammer packing flat if it's the correct size to get it in, If you did then it must have been a size too big which 'WILL' tighten it up. Was the shaft nice and free to turn when the old packing was removed? If it still overheats with the correct size packing fitted with the gland nuts done up 'just so' then either the shaft and or tube bearing is either badly worn or it's badly out of alignment with your gearbox output coupling or whatever flexible coupling you have.

 

You got me thinking, why should I hammer the packing down. I searched the basement and found some 5 mm packing. 6 mm was actually too big.

 

Put in the 5 mm packing while the boat was in the water. Not a drop of water came out while doing so. Is that OK? Now the gland still gets warm to hot. After running for about 15 minutes it reaches a temperature which seems to stay the same. I am not sure if that is too hot. I can still touch the gland and keep my fingers on it without burning myself. Could it be that this will run itself in after a while?

I would like to get a bit sailing in this fall. I plan to check the alignment in the spring or when the weather gets warmer.

Am I correct with this: In order to check the alignment I must take off the flexible propeller shaft coupling (buhk) and replace it with a solid coupling to measure the gab. In this case I would have to buy myself a solid coupling. Is there a way to do it without removing the flexible coupling? I could borrow a dial gauge indicator if necessary.

Thanks Doug

[X Alan W]

Is the packing at the prop end still fitted? If yes I would try removing it, it could be stopping the grease from passing the full length of the outboard bearing, Ideally when you have a tide out situation remove packlng & pump grease till it shows on the shaft as it comes out of the stern bush/bearing, run the inboard stuffing collar with the adjustment finger tight. Did you fit 3/4 separate turns of packing ? I ask because i have seen a single piece of packing wound around the shaft 3/4 times & when run up in gear the friction caused the packing to tighten around the shaft causing the inner end of the tube to run extremely hot. Just thoughts that may/may not help.

[walli]

Thanks, yes the packing at the prop end is still fitted. Grease does come out at the stern end. Grease also comes out of the front bearing. (saw that when I had the rubber tube off).

I put in 3 layers of separate packing.

Doug