Slow motion video of my engine and shaft vibration

[BruceK]

Good luck MB1969. I had a bent shaft(on the boat),replacing it cost. Let`s hope its something more easily fixed. Nice clean bilge you`ve got there.

 

[MichaelB1969]

Good luck MB1969. I had a bent shaft(on the boat),replacing it cost. Let`s hope its something more easily fixed. Nice clean bilge you`ve got there.

Thanks Bruce!

 

[Waterford]

I had a mystery vibration on my boat a couple years back. After trying several fixes, the boatyard owner proclaimed it was a bent shaft and that if he was wrong, he'd pay for it himself. His theory proved false and I got a new shaft. I took the boat back without a fix, put on the correct prop zinc and solved the problem. Don't overlook the simple solution.

 

[MichaelB1969]

Had my Volvos serviced a few days ago and he checked the alignment at the engine/shaft coupling and determined that I most likely have a bent shaft. Shaft was pulled at the yard yesterday and is at a prop and shaft shop. Estimate to straighten it was $770. For what it's worth, shaft is 50mm (2"). We'll see what they say. Didn't hear anything today but first step is that they put it on rollers and determine if it's bent or not, and if so, whether or not they can straighten it.

 

[Ski in NC]

Make sure that when on rollers, the coupling is fitted to the shaft and they indicate the face of the coupling too. A few thou out on the coupling face is magnified down the shaft line. Should be 0.000" TIR on face. (total indicated runout, meaning dial needle does not move. Really coupling face should be tested with shaft in a lathe as on rollers axial position is not fixed. But machine shop guys know this stuff.

Standard practice when doing shaft work is after shaft is straightened, shaft is put in a lathe, coupling fitted, and a skim cut made on the coupling face to make it absolutely true. If this is not done, you are getting a partial job. For $770, you don't want partial.

 

[Art]

What do you or anyone else feel bent the shaft... if it turns out to be bent? How's the prop and cutlass bearing?

 

[Marlinmike]

To Ski's point, you really need to go though testing the components before making a prognoses.

Many things can cause a vibration (as stated in other posts), best to find it before going the replacement route.

 

[MichaelB1969]

What do you or anyone else feel bent the shaft... if it turns out to be bent? How's the prop and cutlass bearing?

Prior owner had a minor grounding incident that bent the props. The props were fixed at Osborne Propellers, a reputable shop up in Vancouver.

I guess they missed the fact that the shaft was impacted.

The shaft is currently at bayshipandyacht here in the Bay Area. They've been in business for 40 years and all the local yards use them for prop/shaft straightening. So I assume they know what they are doing. But I will definitely ask the questions you posed Ski in NC! Thanks!

Mike

 

[MichaelB1969]

Make sure that when on rollers, the coupling is fitted to the shaft and they indicate the face of the coupling too. A few thou out on the coupling face is magnified down the shaft line. Should be 0.000" TIR on face. (total indicated runout, meaning dial needle does not move. Really coupling face should be tested with shaft in a lathe as on rollers axial position is not fixed. But machine shop guys know this stuff.

Standard practice when doing shaft work is after shaft is straightened, shaft is put in a lathe, coupling fitted, and a skim cut made on the coupling face to make it absolutely true. If this is not done, you are getting a partial job. For $770, you don't want partial.

BTW, just looked at the quote. The line item says:

2" Propeller Shaft Straighten as needed fit & face coupling​

 

[Nomad Willy]

At first it looked like a bent shaft to me but looking more at the vid it looks like the whole engine, shaft and all is moving right and left .. sideways. But from the position of the camera vertical movement would be harder to detect.

Could be the wrong hardness of rubber in the mounts. Softer mounts at the wrong end. I put my aft mounts on the trans instead of the bellhousing to limit pitching and tail wagging. A bit like a car w longer wheelbase.

Some mounts aren't differential as they allow movement in all directions. Not ideal as engines move mostly from a power pluse happening or a power stroke happening. This accellerates the crankshaft and a compression stroke decelerates the shaft and flywheel. These radial forces causes the engine to rotate this way and then back. Heaving (straight up and down) movement (of the whole engine) is minimal as is pitching and yawing. Radial motion is the problem.

But the radial motion causes up and down heaving alternately from side to side. Right side going up as left side goes (moves) down. All of this boils down to the fact that mounts that move most easily up and down are great and most desirable. The almost exception to this is the mounts being required to deal w all of the thrust of the propeller in both directions.

Perhaps there is some not ideal element of engine installation applied here that needs to be changed. Understanding is the key to trouble shooting.

OP do you know of another boat w the same installation?

 

[MichaelB1969]

OP do you know of another boat w the same installation?

None of the other Swift Trawler 44's that I know of have this issue. Also, my boat has twins, and the other engine doesn't move at all. I assume I will know more once I hear from the shaft shop as to whether or not it was bent, and if so, how much. The boat yard will check alignment upon reinstallation. So we'll soon see if the issue is resolved.

 

[Nomad Willy]

Having twins mostly simplifies trouble shooting.

You could run the boat slowly then shift the shaker into neutral. Use a stick or a dial gauge ... put one end on the shaft and you should get a fair indication of the shaft runout. This way the engine has little input vib wise .. actually less if it's bumped uo to 1400rpm or so.
Or you could manually (you pick a method) turn the shaft at the float w the engine turned off. Should be about the same results.

Oh I see you've already got the shaft out.
Best of luck Michael.

 

[MichaelB1969]

Just got word back from the shaft shop. Said that it is bent, but is repairable. Said that they typically like the shafts to be straight within 2 to 3 thousandths, and my shaft is out 15 thousandths. $990 to repair. The shaft is 50mm.

 

[Art]

Just got word back from the shaft shop. Said that it is bent, but is repairable. Said that they typically like the shafts to be straight within 2 to 3 thousandths, and my shaft is out 15 thousandths. $990 to repair. The shaft is 50mm.

Sorry to hear that... but... good you now know how to stop the vibration before other things go awry.

Well... there goes another "Boat Buck"!

 

[High Wire]

The trans in the video is moving a lot more than .015, like 10x more. Color me skeptical.

 

[MichaelB1969]

The trans in the video is moving a lot more than .015, like 10x more. Color me skeptical.

Could be that the movement is amplified by the flexible engine mounts. They are going to check alignment when the boat is back in the water, then we'll give it a test run to see how things go.

 

[MichaelB1969]

So I picked up the boat today after the shaft was straightened and reinstalled. I was underway and once we got going I opened the hatch to the engine room. I took a peek at the starboard engine and it was no longer shaking. All was well. Phew. I looked over at the port engine, and to my horror it was moving all over the place. If you recall, my port engine was fine, but the starboard engine was vibrating due to the bent shaft.

Apparently, when the boat yard put the boat back in the water and adjusted the alignment on the starboard engine after the shaft reinstallation, they decided to check the port engine alignment too. They said it was way out of alignment and they said they adjusted it. After I returned to the boat yard to tell them that the port engine was shaking, they were a bit bewildered. Their theory was that the port shaft may also be bent, and now that they fixed the alignment, it's causing the engine too vibrate at low rpm. It also looked like it was leaking a bit of water through the shaft seal, which it had never done. I said it hadn't done either before. They said that before when the alignment was off, the shaft was probably moving toward the prop, but now that it is aligned, it is moving closer to the engine.

Does this sound logical?

It's a major bummer.

Note that whereas the starboard engine vibrated more in the midrange, this engine movement on the port side goes away around 1,400 rom but is far worse than the other engine was in terms of movement under 1,000 rpm.

 

[Lou_tribal]

My comment won't help you in any way but reading your story I think the universal joints I have on my boat is not a bad idea at all!

 

[psneeld]

No, I have never heard or read that the shaft moves forward or back due to alignment.

Guess there might be an explanation, but never heard of this.

All the rest sounds plausible, but depending on what shaft seals you have, alignment issues wouldn't make the seal leak unless it was huge.....so that needs a bit of info to see what that issue really is.

 

[Art]

I'm so sorry this happened to you in mid summer. Hoping resolution can be accomplished ASAP.


First thing I recommend... check to see if alignment was done correctly on port engine.

 

[MichaelB1969]

I'm so sorry this happened to you in mid summer. Hoping resolution can be accomplished ASAP.


First thing I recommend... check to see if alignment was done correctly on port engine.

Thanks. That's what is happening this morning.

 

[twistedtree]

Were the alignments all done with the boat in the water? The hull can take on enough of a different shape when hauled and blocked to change alignment. So my understanding is that you want the boat back in the water for 24hr or more to settle back into it's natural shape, then do the alignment.

 

[MichaelB1969]

Were the alignments all done with the boat in the water? The hull can take on enough of a different shape when hauled and blocked to change alignment. So my understanding is that you want the boat back in the water for 24hr or more to settle back into it's natural shape, then do the alignment.

It was back in the water for 24 hours but not sure whether they checked the alignment after 2 or 24 hours as I'm not sure what the sequence of work was. But they definitely did the alignment in the water. That much I do know.

 

[MichaelB1969]

Here is video of the port engine. I think this was around 800 - 1,000 rpm. https://www.icloud.com/sharedalbum/#B0g5VaUrzM1kTu

 

[smitty477]

So I picked up the boat today after the shaft was straightened and reinstalled. I was underway and once we got going I opened the hatch to the engine room. I took a peek at the starboard engine and it was no longer shaking. All was well. Phew. I looked over at the port engine, and to my horror it was moving all over the place. If you recall, my port engine was fine, but the starboard engine was vibrating due to the bent shaft.

Apparently, when the boat yard put the boat back in the water and adjusted the alignment on the starboard engine after the shaft reinstallation, they decided to check the port engine alignment too. They said it was way out of alignment and they said they adjusted it. After I returned to the boat yard to tell them that the port engine was shaking, they were a bit bewildered. Their theory was that the port shaft may also be bent, and now that they fixed the alignment, it's causing the engine too vibrate at low rpm. It also looked like it was leaking a bit of water through the shaft seal, which it had never done. I said it hadn't done either before. They said that before when the alignment was off, the shaft was probably moving toward the prop, but now that it is aligned, it is moving closer to the engine.

Does this sound logical?

It's a major bummer.

Note that whereas the starboard engine vibrated more in the midrange, this engine movement on the port side goes away around 1,400 rom but is far worse than the other engine was in terms of movement under 1,000 rpm.

No - this does not sound logical....
"Their theory was that the port shaft may also be bent, and now that they fixed the alignment, it's causing the engine too vibrate at low rpm."

A correct check of shaft and alignment would have shown this to be the case before they proceeded.

 

[Art]

Here is video of the port engine. I think this was around 800 - 1,000 rpm. https://www.icloud.com/sharedalbum/#B0g5VaUrzM1kTu

Wow - That really, really moves the engine/trany - a lot! Some how I can't figure how the shaft would have been so far out previously without making considerable engine vibration [maybe I should say "drastic movement"] previously, before they aligned it.

Something does not add up here. I know you are checking the alignment they did very carefully. Seems that they left a shim or something in place or out of place to suddenly get that much out of alignment.

Also, and I don't like to even think this... they use slings to lift your boat? Some dummy put too much sling pressure on your port shaft? Would think if that was so then the sling would have been pushing on both shafts.

?????? - Hope you find out soon - ??????

 

[Ski in NC]

Don't panic. To check alignment they had to separate the shaft and gear flanges. Just a little crud between the flanges and you can get exactly what you see.

Pull back the shaft and clean clean clean the mating flanges. Check alignment again while at it.

Did they pull the port prop? Pull the port shaft? If prop is not seated well, it can set up a vibe that will come all the way up the line and shake the engine.

 

[MichaelB1969]

Don't panic. To check alignment they had to separate the shaft and gear flanges. Just a little crud between the flanges and you can get exactly what you see.

Pull back the shaft and clean clean clean the mating flanges. Check alignment again while at it.

Did they pull the port prop? Pull the port shaft? If prop is not seated well, it can set up a vibe that will come all the way up the line and shake the engine.

Well, after waiting to get the boat back after 3 weeks it was very disheartening to see the engine that was perfectly still before now moving around. But I'll try not to panic! Anyways, they did not pull the port prop or shaft.

 

[smitty477]

Well, after waiting to get the boat back after 3 weeks it was very disheartening to see the engine that was perfectly still before now moving around. But I'll try not to panic! Anyways, they did not pull the port prop or shaft.

When they did the alignment that you were not aware of the first step would be to separate the coupling and check the clearances at 3 , 6 , 9 and 12 O'clock positions.
I always shoot for 0.001" or less for every inch of flange diameter but usually can get much tighter.
The second step would be to rotate one coupling flange 90 degrees and recheck the clearances - right there they would see a bent shaft.

So perhaps ask them what they did do as I know a bunch of folks who cut corners here are often disappointed as a result.

 

[MichaelB1969]

When they did the alignment that you were not aware of the first step would be to separate the coupling and check the clearances at 3 , 6 , 9 and 12 O'clock positions.
I always shoot for 0.001" or less for every inch of flange diameter but usually can get much tighter.
The second step would be to rotate one coupling flange 90 degrees and recheck the clearances - right there they would see a bent shaft.

So perhaps ask them what they did do as I know a bunch of folks who cut corners here are often disappointed as a result.

I am sure they did that, but I suppose they might have not done the rotation with no reason to believe the shaft was bent. I am hoping they simply made a mistake as the thought of dealing with another bent shaft kinda sucks!