Is this normal? Shaft movement- short video

Before I ask some follow up questions about things related to the shaft seal, is this shaft movement normal? https://youtube.com/shorts/f4H9Zn3c9eI?feature=share

Specifically asking if the shaft seems misaligned or is this normal movement? I never paid attention to it before. Thanks

It’s hard to tell from just a video. Was that cruising speed? It doesn’t look catastrophic to me but it could be better. I am curious, can you feel the oscillation in the boat?

I don’t think it’s an emergency but I’d check the shaft alignment pretty soon. There are a bunch of YouTube videos on how to do it.

Agree about the speed , need to know.
I've seen worse but that can still be reduced most likely.
THe less wobble the better for the gear box.

That's at the dock, in gear, about 1000 RPM. Idle is less..not sure, maybe 850?

tiltrider1 said:

It’s hard to tell from just a video. Was that cruising speed? It doesn’t look catastrophic to me but it could be better. I am curious, can you feel the oscillation in the boat?

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At the dock, in gear, about 1000rpm. 850 is idle. No vibration evident.

It may not cause vibration but it’s not right. The shaft should not wobble like that. It’s probably not a huge problem but it should be checked as soon as possible to find out the cause.

Ken

It doesn't look like it's too far off, but I would look into it if it was on my boat.

The water under the shaft appears to be rippled.

From the naked eye it looks fairly bad. Maybe put a dial gauge, not sure that is the correct name, on it to see how much it is actually moving. It can be a fairly involved job to make sure the shaft is running true. You can take it to a machine shop to see if it is straight. But it could also be the cutless bearings are not in line. But the easiest thing and the first thing I would do is check the engine alignment and see if that fixes the problem l. But I wouldn’t let it go for very long.

More details about why I asked about the vibration-

Boat launched this morning, this is my first launch as the owner. Boat purchased last year, I was too excited and wasn't looking at anything...call it new boat euphoria?

Well they dropped the boat in, I started it. Did not even get it into gear, and noticed the shaft seal was leaking quite a lot. Not like sinking in 5 mins, but a slow faucet stream. Until today, I really didn't understand shaft seals and how they worked, but I'm learning.

Marina tech says seal is shot, but there's a spare on the shaft. Sweet! Pull into slip, 45 mins later tech comes down, cuts old seal off, slides new one on.

Well the seal still leaks....very very little..but at idle in forward, maybe 1-3 drips per second? Up the idle to 900 or 1000 in fwd, zero leaks. Neutral? No leaks. Reverse at idle, no leaks. I have not taken the boat out. Icebergs still floating around Lake Superior, and the Coast Guard didn't even have their boat in.

Should I be concerned about the leak? Is it because it's cold? 41 degrees and sunny today. Probably colder in the bilge. When they first put it in, it was leaking a lot. Ran at idle in gear, now in current state described above.

Things I do know:
- Shaft, coupler and seal were new in August of 2018. A grounding event by previous owner.
- All work done by a high end marina by previous owner. I have every work order.
- Shaft seal is a "Tides Marine" model K1750. It is this seal exactly: https://www.tidesmarine.com/ws/index.php?route=product/product&product_id=310

I don't think it was leaking at all last year, but I did have a little water down there I just never got around to figuring out.

How concerned should I be? I understand to replace this now since I used the spare is a drop the rudder, pull shaft sort of deal. Also the vibration....how concerned do I need to be? Going to ask the tech to come look at it tomorrow and get their thoughts.

Thanks for you thoughts!

If the boat had a grounding then that would make me more anxious to have it checked out completely. How do you know the yard that did the repairs did it properly? Did they replace or straighten the shaft?

It’s not right and the dripless will wear prematurely. I would be concerned with catastrophic failure of the bellows.

Comodave said:

If the boat had a grounding then that would make me more anxious to have it checked out completely. How do you know the yard that did the repairs did it properly? Did they replace or straighten the shaft?

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The shaft was replaced. The repairs were detailed well and also a focus of my survey when I purchased the boat. No issues were flagged at that time.

I also have all the work orders, and talked to the people that did the repairs. I believe it was done correctly.

So, all ok before hauling out for winter but, not ok on relaunching. Why?
Unsupported load on seal while up? Seal now described as shot. How did it change?
Was alignment checked after an initial period of running? Maybe by PO, via repair techs? Should it have been checked?

Plenty of water has gone under the keel since August 18, and although you understandably got in another tech, having the marina who did the 2018 work take a look makes sense, if feasible.
Either way, alignment needs checking.(Always wondered how shipwrights work to thousands of an inch doing alignments.)

mncruiser said:

The shaft was replaced. The repairs were detailed well and also a focus of my survey when I purchased the boat. No issues were flagged at that time.

I also have all the work orders, and talked to the people that did the repairs. I believe it was done correctly.

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From the bolded I expect that it was a true shaft until coupled with the tranny. That plus it was not aligned in the water after a period of time at rest. Get it aligned while in the water.

mncruiser said:

The shaft was replaced. The repairs were detailed well and also a focus of my survey when I purchased the boat. No issues were flagged at that time.

I also have all the work orders, and talked to the people that did the repairs. I believe it was done correctly.

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This issue should have been flagged. If it is this visible in the video then the surveyor should have seen it.

BruceK said:

So, all ok before hauling out for winter but, not ok on relaunching. Why?
Unsupported load on seal while up? Seal now described as shot. How did it change?
Was alignment checked after an initial period of running? Maybe by PO, via repair techs? Should it have been checked?

Plenty of water has gone under the keel since August 18, and although you understandably got in another tech, having the marina who did the 2018 work take a look makes sense, if feasible.
Either way, alignment needs checking.(Always wondered how shipwrights work to thousands of an inch doing alignments.)

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Maybe all was not ok before. I’m not sure as I didn’t pay a lot of attention to it until now. We ran 50 hours delivering the boat here, and probably another 100-150 with no issues, but again maybe there were but I didn’t notice.

What do you mean by “unsupported load on seal while up”?

I can ask about the alignment by previous techs. Previous marina is in Charlevoix, MI. I’m 50 hours by boat away from them now.

Having it looked at tomorrow for initial diagnosis, will ask for a thorough alignment check beyond my stare.

Some additional observations on vibration.

It’s cold here. 41 yesterday. The engine is a Yanmar 6LP-STE. On cold startup, the boat vibrates a lot, while in neutral. After a long warm up, it settles.

The ripples you see in the water in the video are there when in neutral or in gear. I’d say things actually quiet down vibration-wise when in gear at idle.

The only time I’ve noticed excessive anything is with a rare WOT burst. But between all the noises associated with that, didn’t notice anything crazy.

Check for movement at the transmission output shaft flange and prop shaft flange connection. If you can move it up-down or side to side by hand, something is not right. I'm not sure about your ZF tranmission, but on my old velvet drive (which is a completely different animal), the nut securing the transmission output flange was backing off and this caused the bearing to have insufficient preload, it was rather simple and cheap fix but was causing a lead at the output seal and excessive shaft movement.

Start with a re-alignment before anything else. Always start with the obvious basics. They are often the most overlooked. But that wobbling is not good.

Redhook98 said:

Start with a re-alignment before anything else. Always start with the obvious basics. They are often the most overlooked. But that wobbling is not good.

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That's my take as well. Wobbling like that means there's probably also uneven wear being caused to components along the shaft. The seals and bearings are taking more than just rotational pressure on them, and this might make them likely to fail sooner than expected.

wkearney99 said:

That's my take as well. Wobbling like that means there's probably also uneven wear being caused to components along the shaft. The seals and bearings are taking more than just rotational pressure on them, and this might make them likely to fail sooner than expected.

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Yep, always start from a known baseline before you start throwing money and parts into it. A good alignment should get it baselined to where it "should" be (if that is possible) and can diagnose more proficiently from there. That amount of vibration or wobble is taking a toll on those cutlass bearing/bushings, and maybe the trans seal and bearings as well.

tiltrider1 said:

It’s hard to tell from just a video. Was that cruising speed? It doesn’t look catastrophic to me but it could be better. I am curious, can you feel the oscillation in the boat?

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When I posted this I had only the video to look at. Now I know the boat experienced a grounding and has already worn out a shaft seal. At this point the answer is obvious. This needs to be dealt with. Starting with an alignment is good advice. If that doesn’t solve the problem then I would have the shaft checked, the prop balanced ant the cutless bearing replaced. I suspect there was a good harmonic vibration at cruising speed.

Alignement of the shaft/engine should be done. In fact the alignement should have been rechecked a few days or a week after the boat splashed. FRP hulls are FAR stiffer than wooden boats but they can still change enough to throw an on land alignement out of alignement enough to cause this wobble. THe on land adjustment should be thought of as only an initial setup to be redone later.

My own boat, a heavily built FRP commercial hull twists on blocks just enough to require a touch up after a week. On land the door will be a hair out of alignement and stick.
Once back in the water no more sticking.


Once done then observe for any other needed work.
And get a spare seal even if you don't install it right away, to be done at the next haulout.

I suggest you do a simple diagnostic measurement. This will tell you what is happening without taking the boat out of the water.

1 Using a dial gage (also called dial indicator), measure the runout* of the shaft close to the dripless (!) seal. Do this with the engine not running, turning the shaft by hand.

2 Then loosen the bolts on the shaft coupling at the back of the gearbox and repeat the runout measurement.

If the runout is the same in both cases, this implies a bent shaft.

If the runout goes away in step 2, this implies that the coupling is causing the runout (the coupling is not square on the shaft).

A good mechanic will have a dial gage, or you can buy one:
https://www.amazon.ca/Accusize-Indu...1&sprefix=dial+indicator,aps,127&sr=8-18&th=1

Good luck !
Nick

* Runout - "wobble", how much a circular surface rises and falls when rotated. Runout is the difference between the maximum measurement and the minimum measurement of shaft surface position when rotated 360 degrees.

tiltrider1 said:

When I posted this I had only the video to look at. Now I know the boat experienced a grounding and has already worn out a shaft seal. At this point the answer is obvious. This needs to be dealt with. Starting with an alignment is good advice. If that doesn’t solve the problem then I would have the shaft checked, the prop balanced ant the cutless bearing replaced. I suspect there was a good harmonic vibration at cruising speed.

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Shaft and seal and components were all new after the grounding in 2018. Verified with work orders and a conversation with the tech this morning. Alignment would have been performed out and in the water.

Maybe it was done incorrectly then? The boat did sit all of 2019 and 2020 inside heated storage. I purchased spring 2021. No issues noted then, but I didn’t really know what to look for.

Nick F said:

I suggest you do a simple diagnostic measurement. This will tell you what is happening without taking the boat out of the water.

1 Using a dial gage (also called dial indicator), measure the runout* of the shaft close to the dripless (!) seal. Do this with the engine not running, turning the shaft by hand.

2 Then loosen the bolts on the shaft coupling at the back of the gearbox and repeat the runout measurement.

If the runout is the same in both cases, this implies a bent shaft.

If the runout goes away in step 2, this implies that the coupling is causing the runout (the coupling is not square on the shaft).

A good mechanic will have a dial gage, or you can buy one:
https://www.amazon.ca/Accusize-Indu...1&sprefix=dial+indicator,aps,127&sr=8-18&th=1

Good luck !
Nick

* Runout - "wobble", how much a circular surface rises and falls when rotated. Runout is the difference between the maximum measurement and the minimum measurement of shaft surface position when rotated 360 degrees.

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What’s generally the accepted amount of runout on a shaft?

Your engine is sitting on resilient mounts which are designed to allow some movement to reduce vibration into the vessel structure. This is why the "stuffing box / seal carrier" is mounted on a bellows hose, to allow for this movement. It could be several mm at the engine, and less on the shaft as you move further aft.

It might be worthwhile to check the mount under the injection pump. Most mounts hate fuel, and this mount is often the first to fail. An old mount would not necessarily increase movement on the shaft, and may even decrease movement as the mount "sets" with age.

Seeing how this is just launched and "new to you," an alignment sure could not hurt, especially after letting the boat "settle" in the water after being on the hard all winter.

Otherwise, it is difficult to tell from the video if what you have is excessive. Note also the shaft should move forward under thrust maybe a mm or 2 as well.

Good question - I don´t know - maybe 5 thousandths? (0.005"). This value may be optimistic. Can anyone else give an opinion?

Looking at the video I would hazard a wild guess that you have a runout in the range of 20 - 30 thousandths.

You say all this work was done…. But you don’t know for sure it was done correctly. You weren’t able to run the boat before and after the grounding so you don’t really know exactly how the boat runs when it is setup properly. So KISS principal. Do the simple stuff first. Then work logically through the whole running gear. Checking the alignment is simple, especially if it is well aligned. So do that first. Then I would look over the motor mounts and see if any are collapsed or showing wear. Then it gets tougher. Checking the cutless bearings, etc. it shouldn’t take 10 to 15 minutes to check the alignment once you have all the tools collected. If you have never done it watch a utube video. It really isn’t difficult. But don’t bypass the simple stuff. Troubleshoot in a specific manner and don’t skip things “because the previous yard did it”.