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Stern gland issues


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Afternoon all,

 

I have 2 issues that I am trying to deal with. Firstly, a noise coming from the stern gland which can only be described as a chirping or squealing, not harmonic. As I was concerned with this, the first suggestion was to repack the stuffing box, so I had this done and this was with packed with 1/4 packing even though the original appeared to be 5/16, I was to that this was used as this style of stern tube was difficult to pack with 5/16, I believe this to be a Roy Willerby stern tube etc. When this work was carried out, the boat was in the water and not one drop of water came into the bilge.

 

As this made no difference, I had the boat slipped and checked over, there was no play in anything, the prop is perfect and when turning the shaft slowly, no sign of any noise or grinding etc. There was not time to draw the shaft as the slip was required and this was just squeezed in for a check.

 

As a suggestion, the stuffing box was repacked with 5/16 but had to be hammered flat to get in.

 

2nd issue, the stuffing box appears to be running hot, when I say not, I can hold my hand on it after a good run, but only just. I have tried to back off the nut but this does not seem to make any difference.

 

Questions:

 

Has anyone had any experience with this stern gear and had any unusual noises to deal with?

 

Is it possible that the nut has been too tight and despite backing the nut off, the packing is already compressed too much?

 

Appreciate that I am trying to deal with 2 issues at once here but any advice / suggestions would be truly greatfull

 

Keith

20220529_183350.jpg

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You should measure the gap the packing fits into. Use drills as gauges.

 

The packing is too tight, it should not run any  more than warm. When correctly adjusted the gland should drip up to twice a minute until you use the greaser. You should be able to turn the coupling by hand.

  • Greenie 1
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Hi Tony,

 

Regardless fo the adjustment, the shaft spins freely and I do not see any drips which is why I am wondering if it has been too tight and is stuck there. Good point about using drills as a measure, would this still apply on this system given that the packing has to pass the thread in the tube?

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1 hour ago, kalees said:

Forgot to mention that I also have grease coming in past the nut, I am guessing that this is due to the grease getting hot and thinning down.

 

A stern gland will run hot if the engine has dropped on its mounts. It typically pushes the shaft down onto the base of the gland nut and front bearing, so check the shaft alignment. Often grease leaks from the front of the gland when the packing is getting worn/loose.

 

The female thread in the tube is almost certainly cut into the tube bore, so the drill trick should work. Otherwise, use calipers to measure (a) the od of the shaft and (b) the id of the packing aperture. Take A from B and halve it. That is the packing size.

  • Greenie 1
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45 minutes ago, kalees said:

Hi Steve,

 

It is not harmonic so I am fairly sure that it is not a singing prop. It is more like a squealing bearing.

 

Just an off the wall thought. Although with  a greased front bearing it should not be, but is there any chance you have a Cutless rubber back bearing or maybe a nylon/paxalon one. With no  water feed from the front either might squeal or chirp.

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Hi Tony,

 

No cutlass bearing although I could not comment on the others. The noise that we hear, we have heard on other boats coming by so maybe it is just an anoying feature of this set up! 

 

Have you had much to do with this make of stern gear, if so, is it possible that it is just an anoying feature?

 

Re the stuffing box, I have just spent the morning replacing the packing myself this time. I used the drill trick to measure and 5/16 is correct so this has been used. I cleaned out all of the old black grease as much as possible and re-packed with 3 wraps of 5/16.

 

I have just run in gear on the ropes for about 20 mins and (in the image) green tube is warm or a liitle more than but the brass nuts I would say are hot.

 

I checked the engine mountings as sugested, bottom nut to top and they seem fine. I have not had a chance to check for further allignment as the engine is now hot and I did not want to change 2 things at once to enable a correct diagnosis.

 

When cleaning out the box there was still no water coming through and I have not seen any while running. When adding the 3rd wrap, I have only taken the brass nut in about 3 threads and the shaft spins freely. 

 

Putting my hand down the weed hatch, I do have grease coming out at the prop end of the shaft.

 

Keith.

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Just a further thought on this, is it possible that the 3rd wrap is too tight because it will still be in the threaded area of the tube where the first 2 are past that point. Dont really want to tighten it right up to push it further in without further advise just in case this damages the packing that I have just fitted and I have no more with me at the moment?

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The ID of the threaded section will almost certainly be the ID of the packing tube and a fraction larger than the OD of the pusher so I don't think the thread has anything to do with it.

 

The hot brass nuts suggests the engine mounts have collapsed and the shaft is being pushed down onto the bore in the nut. Time to take the coupling off and check the radial alignment.

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So... after a frustrating afternoon undoing the wrong bolts on the Centa flex coupling, I undid the 8 that hold the coupling together and not the 4 from the gearbox, who knows what I was thinking!!!!

 

Alignment appears to be spot on but the Stuffing box and nut still appear to be getting hot, not quite sure what else it could be?

 

Regarding the Centa flex coupling, it has taken a lot of bolting back together as there appeared to be surpless rubber around some of the edge so have had to keep going around the blots tightening them up. Will this be an issue in the future, do I need to replace the coupling?

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My dad had a Hurth on his boat; rather unreliable even after being exchanged.  Being the mend-anything (and spend nothing)  sort, he took it apart and found that wear in several parts meant lost motion in the engagement.  Spent ages on his lathe creating a complicated eccentric to make up for the lost motion - and was feeling quite pleased with himself when it all worked nicely on the bench.

 

Final stage was to harden the camshaft - for which he used an ancient tin of case hardening powder and his solid fuel fire.  Not so happy when he found the hardening process had shrunk his gadget such that it no longer engaged the gears.

 

Like Tony - I would be looking to see if it can be changed for a PRM

Edited by Tacet
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1 hour ago, Tacet said:

My dad had a Hurth on his boat; rather unreliable even after being exchanged.  Being the mend-anything (and spend nothing)  sort, he took it apart and found that wear in several parts meant lost motion in the engagement.  Spent ages on his lathe creating a complicated eccentric to make up for the lost motion - and was feeling quite pleased with himself when it all worked nicely on the bench.

 

Final stage was to harden the camshaft - for which he used an ancient tin of case hardening powder and his solid fuel fire.  Not so happy when he found the hardening process had shrunk his gadget such that it no longer engaged the gears.

 

Like Tony - I would be looking to see if it can be changed for a PRM

I think you may have replied to the wrong thread?  Interesting though, thanks.

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