Vibrating shaft at slightly high revs.

[hpeer]

As a by note, when thinking about seals, what does it take to replace one? I have a boat that requires the engine to be lifted so the shaft can be slid inboards to remove. Not the most convient arrangement.

[Hoohaa]

Its actually the volvo PSS in the earlier picture that don't make a 1 1/8th". Or at least that is what they told me at my local Volvo dealer (could mention the name here but I'm not shore if I should).
They initially interested me because they actually have a small cutlass type bearing built in.
Dam. Around $500 is what I have been quoted.
Jeff

[Pete7]

Originally Posted by hpeer

As a by note, when thinking about seals, what does it take to replace one? I have a boat that requires the engine to be lifted so the shaft can be slid inboards to remove. Not the most convient arrangement.

Normally the propeller is removed and the shaft slid out the back, hopefully past the rudder. However, if you have a V drive gearbox or something odd then there could be a lot of extra work.

However, I find the Volvo seal lasts about 5 years. Actually the cutlass bearing normally needs changing first which also requires the shaft to come out, so I put a new shaft seal in at the same time.

Pete

[Hoohaa]

I am thinking about the PSS shaft seal and was hoping to get some thoughts or experiences with this type of stern gland on a slightly wobbly prop shaft?
On another note.
I spent the last 3 days resetting all of the engine mounts so that they had (as near as I could)equal loads on all four mounts and then I aligned it to better that 2 thous all round. Its by far the best alignment result I have ever managed to get.
The results are pretty good. I still have a small wobble in the shaft but the nocking is only at around 11rpm. Which means I can actually. For the first time, run my brand new engine up to full rpm's without worrying about what might be happening to the stern tube. Happy days.
I am still going ahead with the additional cutlass bearing and currently debating weather or not to go for a PSS shaft seal?

[Uncle Bob]

Originally Posted by Hoohaa

I am thinking about the PSS shaft seal and was hoping to get some thoughts or experiences with this type of stern gland on a slightly wobbly prop shaft?
On another note.
I spent the last 3 days resetting all of the engine mounts so that they had (as near as I could)equal loads on all four mounts and then I aligned it to better that 2 thous all round. Its by far the best alignment result I have ever managed to get.
The results are pretty good. I still have a small wobble in the shaft but the nocking is only at around 11rpm. Which means I can actually. For the first time, run my brand new engine up to full rpm's without worrying about what might be happening to the stern tube. Happy days.
I am still going ahead with the additional cutlass bearing and currently debating weather or not to go for a PSS shaft seal?

Jeff, hi have you considered a simple pillow block bearing on the shaft just near the stern gland, grease-able, inexpensive and in your case readily accessible. It would keep the shaft running true without loading the forward end of the stern tube. These bearings can be found in any bearing supply virtually anywhere, they are made as vertical or horizontal mount and are self aligning within the mount.

[Hoohaa]

Gday Bob
Yes, I have looked at that idea.
The bearing would need to be placed about 150 to 200mm closer to the gear box ie. Closer to one end of the shaft and require a bit of work to mount it. Its an option but the longer i've been looking at the cutlass bearing idea the better I think it is.
The cutless bearing will be A little bit closer to the center of the shaft, so should have a better chance of supporting the shaft right where its needed. It will also center the the shaft in the end of the stern tube. Taking the guess work out of the alignment.
Also, Thanks for putting me onto the WM Diesel. It's a cut above the others for shore.

[Uncle Bob]

Originally Posted by Hoohaa

Gday Bob
Yes, I have looked at that idea.
The bearing would need to be placed about 150 to 200mm closer to the gear box ie. Closer to one end of the shaft and require a bit of work to mount it. Its an option but the longer i've been looking at the cutlass bearing idea the better I think it is.
The cutless bearing will be A little bit closer to the center of the shaft, so should have a better chance of supporting the shaft right where its needed. It will also center the the shaft in the end of the stern tube. Taking the guess work out of the alignment.
Also, Thanks for putting me onto the WM Diesel. It's a cut above the others for shore.

You'r welcome, I really didn't think red was your colour.

[jimbunyard]

Originally Posted by Hoohaa

I am thinking about the PSS shaft seal and was hoping to get some thoughts or experiences with this type of stern gland on a slightly wobbly prop shaft?
On another note.
I spent the last 3 days resetting all of the engine mounts so that they had (as near as I could)equal loads on all four mounts and then I aligned it to better that 2 thous all round. Its by far the best alignment result I have ever managed to get.
The results are pretty good. I still have a small wobble in the shaft but the nocking is only at around 11rpm. Which means I can actually. For the first time, run my brand new engine up to full rpm's without worrying about what might be happening to the stern tube. Happy days.
I am still going ahead with the additional cutlass bearing and currently debating weather or not to go for a PSS shaft seal?

Glad to hear you've gotten close to good enough.

Not sure if anyone else's brought this up, but I doubt that Sigma will warranty their drive if you have any problems using it as you're suggesting; with a rigidly mounted shaft.

The sigma drive is meant to provide accommodation for coaxial misalignment, where two axes are up to 8 degrees out of alignment. It is not meant to allow for lateral movement of the engine in relation to a rigidly positioned shaft.

You might be able to get away with this with very stiff motor mounts, but there is at least some possibility that the shaft will eventually break.

If you want to go with a rigid shaft mounting, then you need two Sigma drives mounted on a shaft, which is then bolted between the propeller shaft and the transmission.

Some pictures from the Sigma brochure...






Not trying to be a spoil-sport, just hoping to inform...

[Hoohaa]

Thanks Jim.
I understand what you're getting at. I still have about 600-800mm or 2ft plusd of exposed shaft between the cutlass bearing an Sigmadrive which will allow a little bit of flex. But critically, I haven't got rid of my old coupling. I use it each time I do an alignment and my alignment skills are improving allot. So once I have it aligned using the old coupling I then remove it and reinstall the Sigma. So I think its not really going to be working too hard. I hope.

[Hoohaa]

Also. I have ordered a PSS Shaft seal. The deciding factor was the ability to add water directly into the bearing as there's a possibility that the new cutlass bearing may restrict water flow to cool the stern gland. So decision made.

[ferrailleur]

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.

I know it's an old post. Thanks anyway:
My Catalina 27 prop shaft hang on the lower part of the stern tube. The cut less bearing is OK (no play = tight). I haven't tried to align the flanges. The boat is on the hard.
I don't see how moving the engine up or down for perfect flanges clearance is going to move up the prop shaft up the stern tube?
The prop shaft is locked up on the strut/cut less bearing.
How does that work?

[Cheechako]

Originally Posted by ferrailleur

I know it's an old post. Thanks anyway:
My Catalina 27 prop shaft hang on the lower part of the stern tube. The cut less bearing is OK (no play = tight). I haven't tried to align the flanges. The boat is on the hard.
I don't see how moving the engine up or down for perfect flanges clearance is going to move up the prop shaft up the stern tube?
The prop shaft is locked up on the strut/cut less bearing.
How does that work?

Do you have a strut also I assume?
It sounds like your strut bearing isn't aligned with your hull cutlass bearing very well. If you have both.? You probably need to remove and realign the strut.

If no strut, then by taking the engine loose from the connecting flanges, the shaft will seek it's best center in your cutlass bearing. (If you have a strut also, That will be determined by the pressures from your strut and your hull bearing.)
Then if you align the engine to put no pressure on the shaft, with the mating flanges concentric and even gap, it will be as good as it's going to get .

[ferrailleur]

Originally Posted by Cheechako

Do you have a strut also I assume?
It sounds like your strut bearing isn't aligned with your hull cutlass bearing very well. If you have both.? You probably need to remove and realign the strut.

If no strut, then by taking the engine loose from the connecting flanges, the shaft will seek it's best center in your cutlass bearing. (If you have a strut also, That will be determined by the pressures from your strut and your hull bearing.)
Then if you align the engine to put no pressure on the shaft, with the mating flanges concentric and even gap, it will be as good as it's going to get .

Thanks for your great answer...
I never experienced any suspicious vibrating in the drive train but after soda blasting the hull I discovered gelcoat cracks around the stern tube and the strut. (pics).
No way I will rebed the entire strut!
I will disconnevt the flanges and see where the prop shat wants to go... and check below (stern tube and cut less bearing).
What else?
Thanks a million.

[Cheechako]

Wow, that's some suspicious cracking. It looks like improper stern tube installation to me. Possibly vastly over catalyzed resin or gel coat for those big cracks. Strut also. It may just be the gel coat if you are lucky.
What I would do is grind that cracked area back removing the gel coat, maybe 1/8" deep, and see what's under there. Someone may have just did a huge Bondo build up. If that's the case it will be pink, or pale green or even snow white under there. Gouge it all out until you get to glass.

At any rate I would remove all the cracked area and laminate some glass back in the part you gouge out. Grind smooth after. It would be a shame not to align the strut if you go that far. They can be bent a bit with a blow or two from a big hammer.
It appears you have no cutlass in your hull (?) so if the engine is disconnected, the shaft should sit even in the strut cutlass.

[ferrailleur]

Originally Posted by Cheechako

Wow, that's some suspicious cracking. It looks like improper stern tube installation to me. Possibly vastly over catalyzed resin or gel coat for those big cracks. Strut also. It may just be the gel coat if you are lucky.
What I would do is grind that cracked area back removing the gel coat, maybe 1/8" deep, and see what's under there. Someone may have just did a huge Bondo build up. If that's the case it will be pink, or pale green or even snow white under there. Gouge it all out until you get to glass.

At any rate I would remove all the cracked area and laminate some glass back in the part you gouge out. Grind smooth after. It would be a shame not to align the strut if you go that far. They can be bent a bit with a blow or two from a big hammer.
It appears you have no cutlass in your hull (?) so if the engine is disconnected, the shaft should sit even in the strut cutlass.

Thanks.... I grinded all the cracks.... I didn't have to go too deep to find even gelcoat (no fiberglass).
Don't have pics of my recent work.
Note that there was no visible cracking inside the hull.
Would hate to move the position of the strut!!
I plan to refill these cracks and apply 2 coats of epoxy base coats on the hull.
Yes, there is a cutlass bearing in the strut.... like I said (?): the shaft is tight=the bearing is OK.