Vibrating shaft at slightly high revs.

[Hoohaa]

Gents. I will be updating very soon as the Sigma drive has arrived.
But I need some help with my stern gland stuffing box which has started to dribble quite a bit more than i like.
Not having ever messed with it myself before. I am hoping someone could give mea quick run down and a sketch of how it works.
I think that the 2 large nuts need to be tightened towards each other but if you look at the picture there does not appear to be any adjustment left in it.

[Hoohaa]

[Chenega]

Originally Posted by Hoohaa

Attachment 167502

In the photo, the nut to the left is the lock nut. Break it free from the packing nut on the right. Tighten the packing nut which will compress the packing around the shaft just till the drip slows to about one drip every minute or so. A half turn...
Re-tighten the lock nut against the packing nut on the right so it won’t spin off when under power in revise.
*this would be a good time to replace the packing if it’s been a while since done.

[Hoohaa]

Thanks Chenega
We the penny dropped the second my wife read the words lock nut.
Thanks again for the quick reply. This forum never lets me down.
All fixed and the studfing box was repacked about 8 months ago by a mechanic. Obviously not by me.
Can it be done while on the water? Very quickly I assume.

[Chenega]

Originally Posted by Hoohaa

Thanks Chenega
We the penny dropped the second my wife read the words lock nut.
Thanks again for the quick reply. This forum never lets me down.
All fixed and the studfing box was repacked about 8 months ago by a mechanic. Obviously not by me.
Can it be done while on the water? Very quickly I assume.

Best done out of the water... but it can be done by replacing only two of the three layers. But if done 8 months ago you should be set.
The sigma drive fixed similar issues I had with my Morris Leigh. Best of luck and let me know how it goes.
SV Fascination, Lyme Ct.
Bfree

[delmarrey]

Originally Posted by Hoohaa

Gents. I will be updating very soon as the Sigma drive has arrived.
But I need some help with my stern gland stuffing box which has started to dribble quite a bit more than i like.
Not having ever messed with it myself before. I am hoping someone could give mea quick run down and a sketch of how it works.
I think that the 2 large nuts need to be tightened towards each other but if you look at the picture there does not appear to be any adjustment left in it.

Here is the Ozzy way of doing it.
https://youtu.be/YxWlKgiCvOA

The thing to remember is to check it again after the next run.

[sailah]

Having just read this entire thread, admittedly skimming some of it, I'd be checking the shaft for running true. Yes I know it was "replaced" but that doesn't mean it's straight. More often than not, they are not straight from the factory and require heat straightening before machining the taper.

I'd set it up on rollers and a dial indicator will tell the tale.

Obviously a big deal to pull shaft but if it's not running true nothing else will work.

Here's a good intro to what it takes to straighten a shaft to a couple thou (0.04mm)

He has a whole series on shafting I have found very helpful

https://www.youtube.com/watch?v=MtnkkAzRgP0

[Hoohaa]

Update..
I have my new Sigmadrive but stupid me ordered the wrong diameter 1" should have been 1 1/8th.
Waiting patiently for the new part to arrive.
Here's the happy snaps.

[Hoohaa]

Update.
Thought I should summarize what’s gone on.
- I have always had a wobble in my prop shaft.
- New shaft plus realignment. Not fixed
- Wobble is present even when you turn the shaft by hand
So this rules out any balance issues or resonance off the hull.
- Propeller was replaced and another shaft realignment (raised the motor about
20mm or 3/4"). Improvement but this was due to the shaft being pushed up
against the top of the stern tube when the engine was raised. Not fixed.
- New engine, engine bed and mounts. Realigned and still not fixed. Worse than
ever. Realigned about 3 times. No good.
- GILow. I realigned and bolted the metal coupling directly to the gearbox
without the Flexible coupling. No improvement. Its wasn't the coupling. It
was chewed up around the edges so it would clear part of the engine cover..
- Rather than buying a new flexible coupling, I bought the Sigmadrive and
finally installed it.

The Sigmadrive has had a drastic improvement almost eliminating the wobble. I would rate it at a 90% improvement. It’s not perfect but its close.

When almost all is said and done, I think the wobble has been caused by having almost 2.3m of unsupported shaft. Or, I am hopeless at alignments.
Currently the Sigmadrive is compensating for any misalignment and or sag in the shaft.
Next time she is out of the water I'm going to install the correct cutlass bearing into the stern tube, maybe both ends and or a pillar bearing in front of the stern gland if that doesn't fix it completely.

A really big thank you to everyone who has contributed and I will post again when she is eventually slipped.

Here is the new Sigma drive in action. Really sorry about the poor quality video.
Also, yes the old coupling is still on the shaft. We need to shift an anode to take it off. In the meantime its working ok where it is.

https://www.youtube.com/watch?v=lExjUgOsGLU

https://www.youtube.com/watch?v=hkZucvlsPdg

[Cheechako]

2.3 meters of unsupported shaft? Yeah, that's a problem! 7.5 feet!

[capt.blain]

Originally Posted by 01kiwijohn

My experience, most likely alignment. Insure shaft is centered before connecting, then check flange face alignment. It requires patience to repeatedly check, measure, then adjust the engine mounts; stay calm, do it right, be satisfied.
Let me know you need more help.

Mine too. The phantom vibrations seem to go away after re-alignment. Sometimes they come back after reversing. My experience is to check the engine mounts. Take the nuts and washers off and make sure the holes are round and not oblong or worn side-to-side. Happened to me.

[Cheechako]

That should have had a pillow block in it to start with. It's not a very big diameter shaft right? 7.5 ft unsupported is a no-no.

[Hoohaa]

I took the boat out on Sunday night to look at VIVID on Sydney Harbour. My first real test on the Sigmadrive.


The nocking was previousley at the front of the stern tube and has now moved to the rear of the stern tube.
I think this is a direct result of the Sigmadrive having a significant effect locally on the front portion of the shaft.
I already have a cutlass bearing at rear of the stern tube but I know it is not correctly sized, so has never really done anything. As can be seen in this picture. If you zoom in on the stern gland you can see the shaft sitting towards the bottom of the stern tube.

So. I can slip the boat and
- Install a new cutlas bearing at the rear of the stern tube.
- I could also instal a new cutlas bearing in the front of the stern tube but am
not shore if this is a good idea or not?
- Another option is to install a pillar bearing imediately forward of the stern
gland.

What are your thoughts?
Here is a sketch of the current situation.

[Cheechako]

Pillar bearing. We call them "pillow" blocks or bearing here.

[a64pilot]

Is that an Autoprop? If so those things are real heavy, and I’m thinking the prop maybe the source of the vibration, maybe cause it’s so heavy