Alignment check

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fryedaze

fryedaze

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Fryedaze
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MC 42 (Overseas Co) Monk 42
I had a yard check my shaft coupling alignment recently. The yard reported that both engines were out by .008. The front of both engines need to lower. Problem is that the mount nut has no further adjustment. The engine needs to be jacked up and a thinner nut installed.
I had it checked due to a minor vib at higher RPMs. It turns out the props are out a little too.
Looking for thoughts on the alignment. The alignment was done in the water.
 
Is 8-thou out of spec? We had ours done a few years ago, so I don't remember what our yard said was beyond acceptable spec of the best alignment. Ours was way off and we had to get larger holes cut in the mounting brackets to get it to go far enough over. Yours seems like a lot of money for 8/1000s... but if it is out of spec... by a lot... you should do it. If it is just 1 or 2 thou, it could probably wait until next trip when you have more to do. Are you going to have the props pulled a trued? Have you already fixed that and done a test run?
 
Not a good idea to do an alignment on blocks. All hulls flex a little. 0.008" is not horrible.

Also, depend on how your shaft is run and how much wiggle room you have there, you may be able to dial it in by raising the back.

Make sure to clean clean clean the coupling mating faces. Amazing how a little crud there can kick out the shafts and cause vibes.
 
It's good that the alignment has the engine close to the bottom of the isolator (mount).

You can remove the nuts and use shims if necessary to drop the front of the engine.
 
When we rebuilt the engine I replaced the engine mounts. After a couple weeks while trying to do the final alignment, we had the exact same problem. The mechanic came back from his truck with a 3’ 2x3” piece of maple. We were able to raise the front of the engine off the mounts to put on thinner nuts. It’s amzing how much you can lift with a lever.
 

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psneeld said:
It's good that the alignment has the engine close to the bottom of the isolator (mount).

.
Click to expand...

Not necessarily.....My summer marina guys insist that near the upper end of the stud is better.

They are experienced in that, I am not.
I'm sure there are arguments either way.
Chevy or Ford I suppose (or should I say Toyota or Honda).
 
Like always...different thoughts...

Actually, most people, including yards, really don't do the total engineering necessary so picking an average isolator will give average results. Thats assuming the performance specs are optimized for the engine to be near the middle of the adjustment range...up or down isn't necessarily better.

My choice is lower because as the mount detriorates, better lower and less movement than higher and more.
 
The specs on my Vetus mounts suggest that it is preferable to have them adjusted at the lower end of the range. Different designs may vary so check with manufacturer.

In regard to being 8 thou out, I wouldn’t get too excited about that, especially measured on the hard. It may be less than that when back in the water.
I’d tune the props first then check for vibration before adjusting the alignment in the water if necessary.
 
Alignment check done in the water is the proper way to do it as Ski points out.
What is the coupling diameter?
Typically a guideline is 0.001" out per inch of coupling diameter is OK. Of course closer is better and can usually be done.

Is there ANY movement in the lower nuts at all? 0.008 at the coupling may only need 0.001 or 0.002 drop at the engine front to at least get much closer.
The distance between the front and rear mounts will have an effect on how much the front really has to drop.
 
Current plan is to tune props and see how she runs. Probably will wait until June to attack alignment.
 
Ski in NC said:
Not a good idea to do an alignment on blocks. All hulls flex a little. 0.008" is not horrible.

Also, depend on how your shaft is run and how much wiggle room you have there, you may be able to dial it in by raising the back.

Make sure to clean clean clean the coupling mating faces. Amazing how a little crud there can kick out the shafts and cause vibes.
Click to expand...
Alignment check was done in water. Yards said raising aft end of engine won't work.
 
I just had my props scanned and rebuilt. Won’t be able to tell how much difference that will make until we launch in the spring but it has to help since one blade on each was out quite a bit.
 
C lectric said:
Alignment check done in the water is the proper way to do it as Ski points out.
What is the coupling diameter?
Typically a guideline is 0.001" out per inch of coupling diameter is OK. Of course closer is better and can usually be done.

Is there ANY movement in the lower nuts at all? 0.008 at the coupling may only need 0.001 or 0.002 drop at the engine front to at least get much closer.
The distance between the front and rear mounts will have an effect on how much the front really has to drop.
Click to expand...

Checks done in water. I am not at boat but I think the coupling is probably 6" and shafts are 2"
 
jleonard said:
Not necessarily.....My summer marina guys insist that near the upper end of the stud is better.

They are experienced in that, I am not.
I'm sure there are arguments either way.
Chevy or Ford I suppose (or should I say Toyota or Honda).
Click to expand...


Near the upper end of the stud? That flies in the face of conventional wisdom, and most motor mount manufacturer instructions, better to be closer to the middle or lower (with room for adjustment) to reduce thrust leverage. The good news is if you are too high on the stud you can always add a shim.

Ski is right, under no circumstances should a final alignment be done when hauled, boats are far too flexible for this. The rule of thumb for coupling clearance is 0.001" per inch of coupling face diameter, so if the coupling was 6", a max of 0.006", if you are truly at 0.008 it's hardly worth changing, but if you are 0.008" over the max, that's worth correcting.

As an aside, and contrary to popular belief, because it's constant, misalignment is rarely the cause of vibration. Eccentrics cause vibration, a bent shaft, bent prop, off center coupling bore or pilot bushing etc. I've encountered many shafts that were so far out of alignment that they could not be turned by hand, and no vibration.

A two part article on alignment

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

https://stevedmarineconsulting.com/the-ins-and-outs-of-shaft-alignment-part-ii/
 
Steve DAntonio said:
Near the upper end of the stud? That flies in the face of conventional wisdom, and most motor mount manufacturer instructions, better to be closer to the middle or lower (with room for adjustment) to reduce thrust leverage. The good news is if you are too high on the stud you can always add a shim.

Ski is right, under no circumstances should a final alignment be done when hauled, boats are far too flexible for this. The rule of thumb for coupling clearance is 0.001" per inch of coupling face diameter, so if the coupling was 6", a max of 0.006", if you are truly at 0.008 it's hardly worth changing, but if you are 0.008" over the max, that's worth correcting.

As an aside, and contrary to popular belief, because it's constant, misalignment is rarely the cause of vibration. Eccentrics cause vibration, a bent shaft, bent prop, off center coupling bore or pilot bushing etc. I've encountered many shafts that were so far out of alignment that they could not be turned by hand, and no vibration.

A two part article on alignment

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

https://stevedmarineconsulting.com/the-ins-and-outs-of-shaft-alignment-part-ii/
Click to expand...
Thanks Steve, BTW I have already read your articles several times. Good info
 
.002" has been my standard since my dad, a chief engineer, taught me. I've fixed a lot of other peoples boats done to a looser standard. I owned more boats than I can list from memory, and several had many thousands of hours. In all that time, I only had to change one of my own bearings.
Depending on the motor mount, you can remove it and take some off the bottom/top, depending on the engine, take some off the engine, or take some off the engine bed.
 
fryedaze said:
Thanks Steve, BTW I have already read your articles several times. Good info
Click to expand...

OK, glad it was helpful. I often tell owners, even if you aren't doing the work yourself, it pays to understand how it should be done. This enables you to ask the right questions to vet a mechanic you are considering having do the work. If you get the wrong answers you can move on. Once the work starts, if you are monitoring you'll know if something's not being done right.

I was on a commercial project in Baltimore last week and was horrified to see a professional mechanic using a "bang nut", a bronze nut screwed to the end of a shaft that's repeatedly slammed with a maul, the shock from which separates the prop from the shaft. That shock is also conveyed into the transmission. It's a shortcut at best. Props should be removed using mechanical or hydraulic prop pullers.
 
I have an old boat, my boat uses shims not nuts. I would imagine you will be chasing nut based alignment for the duration of the ownership of the boat. I have lots of shims. Big shims, small shims, paper thin shims and 1/4" shims. Like I said I have an older boat. When aligning I would love the ease of a nut to make it perfect but, how long will it last?
 
I'm no fan of flex couplings, I've seen too many fail and I believe it encourages sloppy alignment.

In order to carry out an alignment, the flex coupling must be removed, none that I've seen have surfaces that are true enough to check alignment. Doing this requires that you be able to pull the couplings together with the flex coupling removed. If Spurs are installed, that may not be possible. As an aside, Spurs sells a precision shim that can be installed to gain the necessary clearance for Spurs installation. That same shim can be used to replace a flexible coupling.
 
Just an fyi as to aligning a flex... Maybe not all are as easy as PYI's.



Flexible Shaft Coupling Installation Instructions


  1. Roughly align engine and stern gear without flexible coupling i.e. only two rigid half couplings pushed together.
  2. Bolt the R&D Marine coupling between the two rigid couplings. Tightening details as below.
  3. Check alignment of the engine by placing feeler gauges between the Red Cone Headed Bolt and the rigid half coupling. Repeat for the Same bolt at 90 degrees intervals by rotating the shaft.
  4. If the gap is the same in all four positions, the engine is accurately aligned. Recommended minimum to maximum gap difference 0.010 inch/ 0.25 mm.
  5. Run installation to bring engine compartment to working temperature. Re-check torque settings.
Click to expand...


https://www.pyiinc.com/flexible-shaft-couplings.html
 
For clarification. Did they say the alignment is 0.008 or did they say it was out by 0.008?



When I do gen alignments we have a max total of 0.005 out. If it were 0.008 out. That would mean the actual alignment is 0.013
 
Steve DAntonio said:
I'm no fan of flex couplings, I've seen too many fail and I believe it encourages sloppy alignment.

In order to carry out an alignment, the flex coupling must be removed, none that I've seen have surfaces that are true enough to check alignment. Doing this requires that you be able to pull the couplings together with the flex coupling removed. If Spurs are installed, that may not be possible. As an aside, Spurs sells a precision shim that can be installed to gain the necessary clearance for Spurs installation. That same shim can be used to replace a flexible coupling.
Click to expand...
When you say that you have seen many failed couplings, is it your experience that they fail from ordinary use, ageing out so-to-speak? I ask because I just experienced a failure when attempting to back off a sand bar I found at a very low tide exiting an anchorage. I assumed I had backed into another part of the bank causing the coupling to break but I had hardly moved, felt no "motion stop", and my other shaft stayed coupled. Plus, my DeFever 44's props sit above the bottom level of the props and are thus somewhat protected so I am suspicious that the coupling failure (Globe Drivesaver) was coincidental. I am hoping it was coincidental cuz I, of course, am also concerned about prop damage.

Also, after being towed off the bar after a rise in tide, I motored 39 miles to a marina on one engine. It was a slower trip as set the RPM at 1,400 which gave me an average speed of 6 MPH. And, no, the parted shaft did not turn moving through the water and it was secured in place just in case. The boat ran quite smoothly.

I have a replacement on the way, two ordered to have a spare on board. Fortunately, on my boat the fix is easy. No more than a one-hour job.

Don't couplings have a service life as well? Also, would you recommend removing the couplings and installing a spacer machined to fit that space? I do have line cutters installed so there would be that issue.
 
Steve DAntonio said:
I'm no fan of flex couplings, I've seen too many fail and I believe it encourages sloppy alignment.

In order to carry out an alignment, the flex coupling must be removed, none that I've seen have surfaces that are true enough to check alignment. Doing this requires that you be able to pull the couplings together with the flex coupling removed. If Spurs are installed, that may not be possible. As an aside, Spurs sells a precision shim that can be installed to gain the necessary clearance for Spurs installation. That same shim can be used to replace a flexible coupling.
Click to expand...

Thanks for the info about the Spurs Spacer. I have been looking for something like this so that I can do a proper alignment on my engines. I have the savers on my engines. I can’t go without something since my shafts aren’t long enough to remove the savers and slide the shafts forward. I am going to look into the Spurs Spacers.
 
catalinajack said:
When you say that you have seen many failed couplings, is it your experience that they fail from ordinary use, ageing out so-to-speak?

SDA: Failed flexible couplings, these vary from an actual coupling that absorbs some misalignment, to insert flexible couplings that are placed between standard shaft and transmission couplings, to Drivesavers. As it happens the bulk of the failures I've seen have been for the Globe Drivesaver, although I've seen failures in all of the above-mentioned flexible couplings. My suspicion is it is misalignment induced, which creates heat and failures. The challenge is the alignment process for virtually all flexible couplings, it's not especially straightforward, and in the case of the Drivesaver, the it needs to be removed to check alignment, so I suspect many of these installations are misaligned.


I have a replacement on the way, two ordered to have a spare on board. Fortunately, on my boat the fix is easy. No more than a one-hour job.

SDA: I would make double sure alignment is correct. Globe Drivesavers are not intended to absorb other than very slight misalignment, their goal is to save the drive in the event of a prop strike (I have never seen one work this way).

Don't couplings have a service life as well?

SDA: Metallic shaft couplings? No, they are forever if properly installed. Flexible couplings are another story, if they are flexing with every revolution, logic dictates they will wear out at some point.

Also, would you recommend removing the couplings and installing a spacer machined to fit that space? I do have line cutters installed so there would be that issue.

SDA: I think you mean Drivesaver, not coupling. Again, I don't see a clear advantage to using the Drivesaver, so you could eliminate it and use the Spurs spacer.
Click to expand...
 
My engine has solid mounts, all adjustments are accomplished with the use of shims. It can be adjusted to a very fine degree, and that does not change when the motor is shifted or revved, as is the case with flexible mounts.
I believe this is where value of the drive saver device lies, it helps absorb the misalignment inherent and inevitable with flexible mount applications.
 
kapnd said:
My engine has solid mounts, all adjustments are accomplished with the use of shims. It can be adjusted to a very fine degree, and that does not change when the motor is shifted or revved, as is the case with flexible mounts.
I believe this is where value of the drive saver device lies, it helps absorb the misalignment inherent and inevitable with flexible mount applications.
Click to expand...

Again I'm dubious of virtually all of the claims for this product (except perhaps that it isolates the shaft from the engine electrically, that it does), however, absorbing misalignment isn't one of them https://www.gcsmarine.com/content/drivesavers/drivesavers

The website also claims they reduce vibration, these are about has hard as the heel of a dress shoe, there's simply no way they reduce vibration.

Even their alignment procedure is flawed.

"With boat in the water, loosen the hardware connecting propeller flange and reverse gear flange so that alignment of engine can be checked using a feeler gauge.

Leave bolts loosely connected during alignment process to support the propeller flange. Align engine installation to .005” maximum by adjusting engine mounts.

After successful alignment, completely disconnect propeller flange from reverse gear flange supporting dead weight of propeller flange."

You can't check alignment with coupling bolts installed, even loosely, you must be able to rotate the coupling faces relative to each other to ensure the gap remains constant.

I can find no mention on the product website of absorbing misalignment.

If you want to do that, you'd use a flexible coupling. The two are very different.
 
fryedaze said:
I had a yard check my shaft coupling alignment recently. The yard reported that both engines were out by .008. The front of both engines need to lower. Problem is that the mount nut has no further adjustment. The engine needs to be jacked up and a thinner nut installed.
I had it checked due to a minor vib at higher RPMs. It turns out the props are out a little too.
Looking for thoughts on the alignment. The alignment was done in the water.
Click to expand...


I'm curious...both engines out of alignment, by the same amount and in the same direction? Was the boat unusually heavily or lightly loaded? I noticed in every alignment procedure I've read, engine manufacturers specify that the boat must be evenly loaded with tanks at about middle capacity or above because hulls normally flex and deform based on loading.



Very interested in hearing expert opinions on this...
 
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