Shaft vibration and scope of work

Swfla said:

Everything has been pointed out to you that could be wrong. You can follow your time frame and splash the boat before every vibration point can be addressed. BUT everyone here is advising against it. In 25 years, I've seen plenty of people delay a bottom job to accommodate their schedule, no danger of further damage. Just delay the haul lout until you have time to do it right. No boating over trawler speed until it's fixed properly. I have a feeling you have a boating trip planned and won't admit that's why you're in a time crunch. You know we'll all tell you to delay the trip. I Hope I'm wrong.

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You're hope came true. He clearly stated all the yards are booked and he would be forced to spend weeks in a hotel. He has followed the advice of just about everyone who has posted. Spending thousands to chase down a barely detectable vibration at X rpm doesn't strike me as a good use of his money.

Thanks for pointing out my oversight/error/lack of thoroughness. I am glad to be wrong as to why.
I agree with your opinion about spending thousands on a barely detectable vibration. But it does seem the he wants to fix it, not sure about the money issue. But, if he's living aboard, it will still cost him more money if it needs to be hauled again. If the motor mounts get replaced later, in the water, won't he need to pull the boat to align the shafts? If that's true, maybe he should delay this haul until he addresses the motor mounts. Doing it in the proper order? Does this make sense to anyone besides me?

Rufus said:

Are you sure the cutless bearings in the hull are not worn? Speaking from experience there is considerable sag/ bending/droop over the length of those long shafts. That can give you incorrect alignment readings at the face of the coupling flanges. And if the front and middle bearings are worn, there’s potential for shaft “whip” under some conditions. If the 42 is the same as the 44, now is the time to replace all of them. That said, the OA yard in Seattle told me they sometimes skip the one by the stuffing box, but then they compensate for the sag at that end when doing the alignment. Not clear who’s doing the work, but checking with the OA yard might be worth the call.

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That's a good point, and something we've discussed. The ones at the struts are in good condition from what we can see, as are the ones at the stuffing box. The ones in the strut are easy to remove with a press tool. The ones at the stuffing box are a pain in the ass, and many people do not replace them because of how difficult it is to get them out as long as they look good. I did talk to OA and that is one of the things they recommended, which sounds like they said the same thing to you!

Swfla said:

Everything has been pointed out to you that could be wrong. You can follow your time frame and splash the boat before every vibration point can be addressed. BUT everyone here is advising against it. In 25 years, I've seen plenty of people delay a bottom job to accommodate their schedule, no danger of further damage. Just delay the haul lout until you have time to do it right. No boating over trawler speed until it's fixed properly. I have a feeling you have a boating trip planned and won't admit that's why you're in a time crunch. You know we'll all tell you to delay the trip. I Hope I'm wrong.

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I don't have a boating trip planned - no hard dates or schedules that are forcing me back in the water. I live aboard my boat, so staying out longer is extremely costly - I think I may have mentioned that somewhere. Plus, there simply isn't room or time for them to accommodate me longer. The yard I'm at is booked out until September 20th, packed so full I have never seen it that way, and they just can't keep adding jobs on without having the boat physically sit for a very long time with no work until someone is available.

My day job is managing complex projects with constantly changing risk. In most situations with yards, I see owners drop a boat off and check in every few days, maybe less. In this situation, I'm 100% focused on the work that needs to be done out of the water, and help refocus them since I am there every day. Replacing the engine mounts is a great example. That needs to be done, but it does not have to be done out of the water. If we get the important things done out of the water, I can continue doing other things dockside or at a later date to improve things.

Marco Flamingo said:

This thread got me to thinking about how to gauge if and whether there is an improvement based on the work done. I recently downloaded an app for measuring sound and have been using it as I work on soundproofing the engine room. I took Db readings at low and high rpm with engine hatch off, hatch on, rug covering, first improvement, etc. Changes are slight but verifiable.

Measuring vibration might also identify a plateau that we identify as a sweet spot in addition to having a vibration baseline.

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Hey this is cool! Thanks for posting this. Some of my concerns about the vibrations I am sure are heightened because of the issues I've gone through, and very well may be no worse than it has been for 2 years! But instead of my subjective standing over the areas and moving around while underway, it would be awesome to be able to measure it. I'll have to look into this once I'm back in the water.

Swfla said:

Thanks for pointing out my oversight/error/lack of thoroughness. I am glad to be wrong as to why.
I agree with your opinion about spending thousands on a barely detectable vibration. But it does seem the he wants to fix it, not sure about the money issue. But, if he's living aboard, it will still cost him more money if it needs to be hauled again. If the motor mounts get replaced later, in the water, won't he need to pull the boat to align the shafts? If that's true, maybe he should delay this haul until he addresses the motor mounts. Doing it in the proper order? Does this make sense to anyone besides me?

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I definitely would like to fix the issue, but I am not willing to spend "anything" to do that. I look at each problem and review with the experts (which includes folks here, folks online, and the yard) what their best recommendations are for the particular problem or section, and weigh how much the work will potentially change the situation compared to the cost. I know some people who will spend anything and replace everything, regardless of the time or cost, and that is a great approach as well, if you can afford both the time and cost. In some ways you may be spending money to replace things or have work done with that approach when you didn't need to. I don't think I'm skipping any steps or areas that have been identified, or not looking at any specific areas - we're trying to make sure we track down everything possible to solve the issue, but of course, it is a boat, so some mysteries take longer to understand than others.

When you replace the motor mounts, you will need to do a new engine + shaft alignment, which has to be done in the water. The shape of the hull changes dramatically when it is out on the hard, and you cannot align it until the boat is back in the water and has settled for multiple days.

That's one of the reasons I've deferred that work for now - the other reason is the yard is so busy they don't have time to replace them right now. But they can do it in October dockside, without a haul out, and do another alignment then, which seems like a great way to get it done without sitting in the yard for 6-8 weeks.

Shafts are aligned in the water, so replacing the mounts in the water is the way to go.

I've never had to do a shaft alignment. Now I know better and it also makes sense to me why Steve is following his path. Steve, I want to thank you for addressing several suggestions brought up and a clear explanation of how you thought things through. It all makes sense to me now. Hoping things go smoothly for you now and in a few months when you finish the work!

You mention the bearings at the stuffing box and the one at the strut, but not clear if the one that exits the hull is within spec....also a big PITA to remove, but pretty critical... I drove it out of the shaft tunnel with a piece of pipe (inserted from the engine room end) and a BFH. The set screws were difficult to locate with all the bottom paint..,

Swfla said:

I've never had to do a shaft alignment. Now I know better and it also makes sense to me why Steve is following his path. Steve, I want to thank you for addressing several suggestions brought up and a clear explanation of how you thought things through. It all makes sense to me now. Hoping things go smoothly for you now and in a few months when you finish the work!

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I've done my own shaft alignments on sailboats which were much smaller, and seemed simpler to me to do in the past. That was a number of years ago, and it took a lot of trial and error to get it right.

Now I let the professionals do it because they know the tricks and how to make something move somewhere easier than I do. I'll still be aboard and watching while they do so I can learn, and watch that the work is done to my expectations, but they are also generally far more flexible than I am to fit into the spaces needed. The guy who will be overseeing it has done it for 15+ years and has done it for me before on a previous boat without any issues.

Rufus said:

You mention the bearings at the stuffing box and the one at the strut, but not clear if the one that exits the hull is within spec....also a big PITA to remove, but pretty critical... I drove it out of the shaft tunnel with a piece of pipe (inserted from the engine room end) and a BFH. The set screws were difficult to locate with all the bottom paint..,

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I can see the set screws for everything which is nice. The traditional way I've been told they remove the bearing that exits the hull is using a sawzall and patience. Cutting it in two spots, folding it up, and removing it. Trying to pound it out from inside is an option but can be very tight - my little hatches to get to that spot are about 10" square, and it would be extremely difficult for one side to be pounded out, if it is even possible.

The stuffing boxes are being replaced, so that bearing will be new. The one that exits the hull looks good from inspection so far, as do the ones in the struts. It is still on the table to replace those as well depending on all of the other work being done. With the shafts out, it would of course be a good time to replace them. They actually look pretty new and are in excellent shape, so guessing they have been replaced in the last 5 years or even less.

I’m sure it depends on the location of the transmission, but on our boat I was able to slide a four or five foot length of pipe/steel rod in from inside the engine room (in the vicinity of the coupling. They were both fairly easy to drive out. In fact the new ones, which I placed in a freezer over night kept sliding out (I had coated them with dish soap). So the fit isn’t that tight. I’d try driving it out before resorting to the sawzall method. Maybe even a big slide hammer with a custom hook.

By the way, the bearing just behind the stuffing box is the one OA suggested could be omitted. It has nothing to do with changing the stuffing box on our 44.
Good idea to change it, but the hull exit ones are about mid span on our boat.

Rufus said:

I’m sure it depends on the location of the transmission, but on our boat I was able to slide a four or five foot length of pipe/steel rod in from inside the engine room (in the vicinity of the coupling. They were both fairly easy to drive out. In fact the new ones, which I placed in a freezer over night kept sliding out (I had coated them with dish soap). So the fit isn’t that tight. I’d try driving it out before resorting to the sawzall method. Maybe even a big slide hammer with a custom hook.

By the way, the bearing just behind the stuffing box is the one OA suggested omitting from renewal. It has nothing to do with changing the stuffing box on our 44.

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Sounds like a good way to do it. I've heard the freezer trick before, and I have used lots of dish soap myself. The yard uses it in gallon sizes

Ok, so just to clarify: the bearing that is directly exposed to the outside and is visible from outside that the shaft goes through is the one you replaced? There's another one (composite I believe you said) behind the packing but inside the stuffing box that you did not replace, and OA says to not worry about?

mike66 said:

Shafts are aligned in the water, so replacing the mounts in the water is the way to go.

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We had an engine and transmission out last winter. After I put it back in we did an engine alignment before we launched. I had thought we would have to do another alignment after we launched. However it was still exactly the same after several days when we checked it after launching. I guess they had the boat blocked almost perfectly when we did the alignment. I was surprised.

Nice thread, just read through it. Fairly satisfying, as the real cause of vibration is “everything”. It’s really the whole ecosystem end to end.

Only thing that stood out to me, or at least I don’t remember reading, is checking whether the strut alignment is good. Basically if the shaft is spinning freely and the shaft is still centered in the log, then you are likely good. Then support it in that position and align the engine to the coupling. The coupling itself CAN be a source of wobble. They should be faced square with the shaft. Not sure if there is an easy way to measure that, The prop shop usually does that when they fit the coupling to a new shaft.

Alignment is always dark arts to me. I turn here, measure. Repeat. Things make perfect sense, then all of a sudden they don’t. Adjust, measure. Adjust, measure. Suddenly everything comes together, but I couldn’t tell you how to repeat the process again if I tried.

Chances are, the mounts simply squatted a bit. Alignment is to a few thousands, doesn’t take much. I bet you do a fresh alignment an she smiles back at you this time.

Yes, I replaced the strut bearing and the middle bearing(where the shaft exits the hull).

There is long stainless steel tube which is fiberglassed into the hull during construction. The shaft runs inside that tube (which is filled with water...some of it injected by the raw water pump to cool the stuffing material). The middle bearing goes inside the aft end of that tube. The forward bearing is inserted inside the forward end of that steel tube. The bare steel end of the tube (with the forward bearing inside) sticks out of the fiberglass structure, and this is where the rubber boot/sleeve/tube for the stuffing box is clamped. Of course the metal stuffing box assembly inserts into the forward end of the rubber tube and is clamped in place. So, the forward bearing is actually independent (although inside the rubber tube/sleeve) of the stuffing box assembly. In other words the stuffing box has to come off IF you want to replace that bearing. I can tell you that the forward end of that long shaft does droop a bit even with new middle and strut bearings, so I made a support for the forward end and lifted it about 1/2” during the alignment process. You wouldn’t think a 2” shaft would distort, but as you know it is a long sucker...even longer on the 44. That’s why OA used three bearings. It does give an absolutely straight shaft run with no chance for distortion along the shaft, but it’s a bugger to refurbish.

If you’re going back to the conventional stuffing box you will obviously want to replace the rubber tubes.

Comodave said:

We had an engine and transmission out last winter. After I put it back in we did an engine alignment before we launched. I had thought we would have to do another alignment after we launched. However it was still exactly the same after several days when we checked it after launching. I guess they had the boat blocked almost perfectly when we did the alignment. I was surprised.

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Wow that is lucky! Or maybe your hull is just super strong/not flexible!

ghost said:

Nice thread, just read through it. Fairly satisfying, as the real cause of vibration is “everything”. It’s really the whole ecosystem end to end.

Only thing that stood out to me, or at least I don’t remember reading, is checking whether the strut alignment is good. Basically if the shaft is spinning freely and the shaft is still centered in the log, then you are likely good. Then support it in that position and align the engine to the coupling. The coupling itself CAN be a source of wobble. They should be faced square with the shaft. Not sure if there is an easy way to measure that, The prop shop usually does that when they fit the coupling to a new shaft.

Alignment is always dark arts to me. I turn here, measure. Repeat. Things make perfect sense, then all of a sudden they don’t. Adjust, measure. Adjust, measure. Suddenly everything comes together, but I couldn’t tell you how to repeat the process again if I tried.

Chances are, the mounts simply squatted a bit. Alignment is to a few thousands, doesn’t take much. I bet you do a fresh alignment an she smiles back at you this time.

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Good points. The shafts both spin very freely and feel good. The props and the shafts aren't new, and they weren't vibrating before too much at all before the strike, so I am going to guess that's not the issue, but it is still something to think about as a potential.

I agree with you on the dark arts. My sorcerer has good energy, so I have good vibes about my alignment!

Given everything we've taken apart, looked at, and gone through, I tend to agree with you - I think the motor mounts are old and things just got out of alignment. Hitting something didn't help, and the vibrations from that probably made the starboard side worse. A fresh alignment will be a good litmus point.

Rufus said:

Yes, I replaced the strut bearing and the middle bearing(where the shaft exits the hull).

There is long stainless steel tube which is fiberglassed into the hull during construction. The shaft runs inside that tube (which is filled with water...some of it injected by the raw water pump to cool the stuffing material). The middle bearing goes inside the aft end of that tube. The forward bearing is inserted inside the forward end of that steel tube. The bare steel end of the tube (with the forward bearing inside) sticks out of the fiberglass structure, and this is where the rubber boot/sleeve/tube for the stuffing box is clamped. Of course the metal stuffing box assembly inserts into the forward end of the rubber tube and is clamped in place. So, the forward bearing is actually independent (although inside the rubber tube/sleeve) of the stuffing box assembly. In other words the stuffing box has to come off IF you want to replace that bearing. I can tell you that the forward end of that long shaft does droop a bit even with new middle and strut bearings, so I made a support for the forward end and lifted it about 1/2” during the alignment process. You wouldn’t think a 2” shaft would distort, but as you know it is a long sucker...even longer on the 44. That’s why OA used three bearings. It does give an absolutely straight shaft run with no chance for distortion along the shaft, but it’s a bugger to refurbish.

If you’re going back to the conventional stuffing box you will obviously want to replace the rubber tubes.

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Gotcha - thank you for all of the detail. There was good news on two fronts today. First was confirmation that both the cutlass exiting the boat and in the strut look like they were replaced 2 years ago from the records we unearthed at the yard (the work just happened to be done here) and with the shafts out, inspection shows them to have 95% of their life left. I am not going to replace those for now.

Second was that the existing shaft seals are in excellent condition. It was the through bolts that tightened things down that were completely falling apart. A little miscommunication there from one of the people working on the boat. I hadn't actually seen them until today after they had cleaned them up, and they look fine. We're replacing the bolts, which should be here tomorrow, and can get the shafts back in, packing in, and things all connected up this week, which is quite a bit earlier than expected.

It was very interesting to see the stainless steel bolts - it was almost as if the leaking water from the shaft because of bad packing / not having it changed over time just pitted and ate away a perfect area on the bolt, and when we were backing them out to take it apart, they just fell apart.

I'll let them know about the distortion with the shaft. They know about the bearing inside the stainless steel shaft log/bearing/tube as they've worked on several other OAs from this vintage, but every bit of info helps on how others have done it.

Am happy to have a shaft only12 inches long and behind a keel.

We have 2 engines and therefore 2 props neither of which is behind a keel. We do however have a keel that does project below the props. When we were bringing our boat up the Hudson we hit countless submerged things, I assume logs and such but the water was so muddy that we never saw any of them. I was sure that my props were trashed but when we got home and hauled out for the winter there wasn’t a nick on them. So much for 1 engine is the only protected props...

Stainless bolts was likely crevice corrosion. If they get wet with stagnant water, they will dissolve in short order. I don’t use stainless below the waterline for this reason. While this is technically not below the waterline, the bolt got wet, wicked into the threads and then sat, that’s all it takes. Above water, with sealant they dry out and have access to oxygen.

Marco Flamingo said:

This thread got me to thinking about how to gauge if and whether there is an improvement based on the work done. I recently downloaded an app for measuring sound and have been using it as I work on soundproofing the engine room. I took Db readings at low and high rpm with engine hatch off, hatch on, rug covering, first improvement, etc. Changes are slight but verifiable.

So what if there was an app for vibration? Turns out that there is (are). I have no experience with them yet (and some reviewers claim that they contain spyware, just like your breakfast cereal box).

Place the phone in a standard location and get high/low rpm reading. Port engine, stbd engine, both (working on synchronization). Now, one would at least have a baseline when the future question of "did the vibration just increase?" issue arises.

One of the things I found with my sound meter app is that the Db reading at 1,500 rpm is basically the same as at a spot near 1,800 rpm. DB was rising (not entirely uniform) and then took a little dip. This might explain the mysterious "sweet spot" we tend to find on a certain motor.

Measuring vibration might also identify a plateau that we identify as a sweet spot in addition to having a vibration baseline.

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What have you used four sound measurements?

Visited today to check on progress. Most of the work the last 2 days has been on prepping the bottom for new coats of Sharkskin as well as removing the many, many layers of random things from the rudders and trim tabs. They look like completely different animals now that they are bare to the metal.



The shaft seals have all been removed and are getting their new bolts today. I wasn't able to get any pictures yet, but I did find that the stainless steel sleeves were bare in the boat now (pictured above) and everything looks fine both outside and inside. They'll be cleaned before the shaft seals go back together.

stevemitchell said:

Visited today to check on progress. Most of the work the last 2 days has been on prepping the bottom for new coats of Sharkskin as well as removing the many, many layers of random things from the rudders and trim tabs. They look like completely different animals now that they are bare to the metal.

View attachment 106280

The shaft seals have all been removed and are getting their new bolts today. I wasn't able to get any pictures yet, but I did find that the stainless steel sleeves were bare in the boat now (pictured above) and everything looks fine both outside and inside. They'll be cleaned before the shaft seals go back together.

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If I may offer a suggestion:
Have the yard (or you if you have time) add a ball valve to the raw water fitting
feeding the stuffing box. A 316 stainless valve with a 316 stainless nipple is best.

That fitting is the equivalent of a through-hull fitting below the waterline and if the
hose were to leak could lead to a lot of water in your bilge. Peace of mind IMHO.

I had a vibration and a rumble and after determining that there were no barnacles in residence, I noted the rudder seemed to have more play than usual. Sure enough the packing gland had backed off and was leaking sea water. I bolted down the clamping collar and the leak stopped, so did the rumble.

Check your rudder packing.

KnotYet said:

If I may offer a suggestion:
Have the yard (or you if you have time) add a ball valve to the raw water fitting
feeding the stuffing box. A 316 stainless valve with a 316 stainless nipple is best.

That fitting is the equivalent of a through-hull fitting below the waterline and if the
hose were to leak could lead to a lot of water in your bilge. Peace of mind IMHO.

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That's actually already planned I replaced them a while ago after seeing how bad they looked, and I couldn't find the right fitting with a valve that matched the strange thread pattern. Not only do I want a valve, but I want enough length for two clamps. I think I may have tracked one down and would do this on my own.

Surprisingly it is not that much water even at rest. The bilge pump easily kept up with it. Still would prefer a valve...

Xsbank said:

I had a vibration and a rumble and after determining that there were no barnacles in residence, I noted the rudder seemed to have more play than usual. Sure enough the packing gland had backed off and was leaking sea water. I bolted down the clamping collar and the leak stopped, so did the rumble.

Check your rudder packing.

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The rudder packing was definitely bad and is being replaced as part of this work. Interesting data point - I never bothered to climb into the laz while at higher speeds to see if the vibration was coming from the rudders but I could totally see that happening!

Thanks!

twistedtree said:

What have you used four sound measurements?

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A free application called Decibel X.

Oh good, rudder vibration. Another thing to check. I wonder if a rudder vibration could transmit through the hydraulic ram all the way to the helm?

Be careful adding a valve to the nipple on the stuffing box because of the weight. Over time the weight may break the nipple off.

Comodave said:

Be careful adding a valve to the nipple on the stuffing box because of the weight. Over time the weight may break the nipple off.

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The 1/4 lb or less of a small ball valve? How so? I guess one could add a strain relief.
There was one on my 46 year old boat that had been there at least a quarter century.

Constant vibration is how so. Doesn’t mean it will but it might. Mine doesn’t have a shutoff and it wouldn’t leak more than my bilge pumps could handle if the hose were to come off. If the hose breaks or the clamp comes off I can easily fix it. However if the barb breaks off that isn’t an easy fix. And I have just replaced the hose on one of mine and will do the other one this winter. The clamps are new AWAB 316 clamps so I don’t see a problem there either.

I have encountered a couple instances of engine vibration caused when the cushy mounts were not equally weighted. Like a four legged table not resting level on the floor the engine will be very sensitive to any slight imperfection in the drive system or other imbalance and rock back and forth against the lightly loaded mounts.

On a trial-run doing engine checks I found an engine mount bottom jacking nut had worked its way down and the engine was busy rocking away. I retightened the nut and as the engine pushed against all four mounts again the vibration receded. Found something similar on a different trial-run.

Careful attention to not only alignment but weight balance on the mounts is important. Some of the mounts have built in indicators to estimate the pressure on them. "Barry" mounts calls that a "snubber gap" per the attached pdf.

Comodave said:

Constant vibration is how so. Doesn’t mean it will but it might. Mine doesn’t have a shutoff and it wouldn’t leak more than my bilge pumps could handle if the hose were to come off. If the hose breaks or the clamp comes off I can easily fix it. However if the barb breaks off that isn’t an easy fix. And I have just replaced the hose on one of mine and will do the other one this winter. The clamps are new AWAB 316 clamps so I don’t see a problem there either.

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If there is constant vibration on the glassed-in shaft log tube - part of the hull -
enough to crack and damage a stainless pipe nipple then there are bigger problems.
Valves can be supported safely and easily if the installation calls for such a support.
The small ball valve, maybe a 3/8" I.D. on my last boat required no such support.

This is an opening in the hull about 3 ft. below the waterline. The rate the sea flows
in depends on the condition of the cutlass bearing. The rate the bilge pump flows out
depends on many factors but should not be assumed to be there when you are away
from your boat for any extended period. What I suggest is just a good preventative.

Before you haul the boat isolate the source of the vibration. SEA TRIAL Put a tech in the engine room and find out if the wiggle starts at the prop and is running up the shaft
Is the coupling wobbling
Engine alignment is never the cause. Good thing to do to reduce bearing wear but thats it.
Also measure your unsupported shaft between the hull bearing (if you have one) and the strut. You can look up the max unsupported shaft for your diameter on the web.
I have seen heavily damaged props with welded in patches that are not detected unless you use the prop scan

Contrary to popular belief, misalignment, because it is a constant, is rarely the cause of vibration.

Shafts can be checked for trueness, to an extent, without removal. A dial indicator can be placed against the shaft in several locations, and the shaft rotated. It's not as definitive as having the shaft in bench rollers, but it's usually good enough to identify an issue. Run out should be measured at the prop taper end as well as close to the coupling, and in a couple of places in between.

Because you mentioned you had the props checked, if the prop does not fully engage the shaft taper, because it is binding on the key, it will not be perpendicular to the shaft, and will lead to vibration.

If the props were not scanned using Hale MRI or PropScan, they should be, the graphic representation they provide is invaluable in assessing prop condition.

Perhaps above all else, the yard you select for vibration analysis must be knowledgeable and experienced in that realm, those with good intentions can spend a great deal of time, and your money, chasing their proverbial tails in attempting to track down the causes of vibration.

These articles may be helpful...

Cutless Bearings: https://stevedmarineconsulting.com/cutless-bearing-etiquette-2/

Alignment How-To: https://stevedmarineconsulting.com/the-ins-and-outs-of-engine-and-shaft-alignment/

Alignment: https://stevedmarineconsulting.com/wp-content/uploads/2014/03/Shaft-Alignment-159-02.pdf

Prop Installation: https://stevedmarineconsulting.com/propeller-installation/