Shaft vibration

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Sno' Dog
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Re: Shaft vibration

Postby Sno' Dog » Fri May 04, 2012 9:15 pm

After reading Captnautigal's account with Catatonic, I decided to try the same thing with Sno' Dog.
We have just completed the same procedure, here's a photo of the completed installation:
Image
In our case, the primary motivation was to eliminate leaking from our TidesMarine shaft seals - which occurred mainly at cruise speed. We assumed that this leakage was caused by shaft vibration.
There is no doubt that the added bearings decrease that vibration. The shafts now run at all speeds with virtually no vibration and the there is absolutely no leakage. The boat now feels noticeably smoother at all speeds. I think this is a very worthwhile modification; and Stuart Yacht is certainly the place to do it. We are 100% satisfied with their work.

Henry
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Re: Shaft vibration

Postby duetto » Sat May 05, 2012 5:52 pm

henry,

i assume that you had stuart do the work. did they have to machine the new cutlass per the earlier post? how did they secure it? did they cut any extra drain slots in new cutlass to make sure water gets to stern one?

we were talking about this mod this winter in marsh harbour. there are 3 of us 34s in the same marina. my question is this: assuming that the engine is jumping around just as it did before and you've effectively shortened the shaft length, what happens?
john & diane cummings
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Re: Shaft vibration

Postby Sno' Dog » Sat May 05, 2012 7:26 pm

I believe they (Stuart Yacht) did exactly the same thing for us as they did for Catatonic. I relied heavily on their previous experience with this specific problem. For a more detailed explanation of exactly what was done, I'd give Gregg Burdick a call: 772-286-9800, I'm sure he'd be happy to explain it.
They did send our shafts out to be straightened, and they did re-align the engines. But as to how the forward cutlass bearings get lubricated, I don't really know. Perhaps from the water fed in by that little tube from the engine?
I suppose the engine "jumps around" as it did before, but there's no doubt that there's less movement of the shaft near the seals. Before, there was noticeable movement there, now there's none.
If you are considering having this done, I'd definitely head for Stuart Yacht. Their prices seemed very reasonable for the work they did, and it's hard to imagine a friendlier, more knowledgeable boat yard.
Good luck,
Henry
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Re: Shaft vibration

Postby Tanah-Keeta » Sun May 06, 2012 11:59 am

Hi Henry,
Can you give us a ballpark number on the cost?
Thanks,
Ron McDaniel
TK III 34108

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Re: Shaft vibration

Postby Sno' Dog » Sun May 06, 2012 1:28 pm

From our Stuart Yacht Harbour LLC invoice - total of parts & labor:

Haul & Launch - $204
Running Gear (chk shafts, straighten stbd shaft, fit & face couplings) - $679
Replace Cutlass bearings - $542
Install new forward Cutlass bearings - $409
Replace Tides Marine seals - $374
Alignment - engines & shafts (new coupling spacers, recondition props) - $933

TOTAL: $3,141.00

As I said, I felt this was very reasonable for the amount and quality of the work done.

Henry
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Re: Shaft vibration

Postby Sno' Dog » Mon May 07, 2012 10:03 pm

Here's a close-up of the new bearing without the Tides Marine seal:

Image

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Re: Shaft vibration

Postby Captnautigal » Wed May 16, 2012 10:12 pm

We've had the boat to the keyes several times. She runs smooth as silk and bilges are bone dry. Very happy with the results! Our favorite upgrade was moving the water heater to the forward starboard hull - it is instant hot water in the shower!!! No wasting fresh water waiting for it to get warm! :)
Maureen (Captnautigal) and David
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Re: Shaft vibration

Postby Captnautigal » Wed Jun 26, 2013 8:08 am

Over a year, several trips to the Keys and one through the Northern Bahamas, from Miami; Catatonics bilges are dry as a bone (no more dripping seals) and no more vibration in the shafts.
Maureen (Captnautigal) and David
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Re: Shaft vibration

Postby jim » Wed Nov 27, 2013 11:15 pm

Maureen, Are you still considering the Aqua Drives or are you happy with the Stuart Marine solution to the shaft vibration? Did Stuart change the engine mounts to softer mounts when they worked on the shafts? Jim
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Re: Shaft vibration

Postby Captnautigal » Wed Dec 18, 2013 9:00 pm

Jim,

Sorry for the late reply. I don't check in often enough here! I am very happy with the 1/2 bearings and no longer considering aqua drives. We've taken many trips to the keys and spent over a month in the Bahamas this summer. The bilges are still dry and vibration has improved significantly since the modification. We still have three bladed props and not considering changing them. Our original engine mounts were in great shape so we did not change them. Overall very satisfied with the results of the 1/2 bearings and realignment job done at Stuart Yacht.
Maureen (Captnautigal) and David
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Re: Shaft vibration

Postby jim » Thu Dec 19, 2013 9:41 pm

Maureen, Thank you for sharing your experience. I believe Sno' Dog had similar shaft support installed at Stuart Marine and also has the four blade propellers. I'd love to hear Henry's thoughts. Jim
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Re: Shaft vibration

Postby Sno' Dog » Sat Apr 19, 2014 6:09 pm

As I just wrote to Duetto in a private msg:

Yes, our added cutlass bearings have, in deed stopped leakage from our Tides Marine seals.
Our bilges have been bone dry since the installation two years ago, about 240 engine hours.
So far, so good. Money well spent!

Henry
www.SnoDogLog.com

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Re: Shaft vibration

Postby Ross Bowling » Mon Apr 21, 2014 10:15 am

No Vibration on Vita Bella, but did swap the Tides Marine for PSS seals, and have not had any leaks for 150 hours.
Ross & Diana Bowling
Vita Bella
PDQ 34-114
Coyote Point Marina,San Francisco Bay

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Re: Shaft vibration

Postby duetto » Mon Apr 21, 2014 2:23 pm

we too switched to pss. they are dry as a bone except when seas get very rough, then we get leaks.

my goal is to eliminate that.
john & diane cummings

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Re: Shaft vibration

Postby DickTuschick » Fri Jun 20, 2014 9:06 am

Hello to all,
I thought it might be time to provide a "recap" on this subject.

Shaft vibration has been an issue on some PDQ 34's and in almost every case it has been traced back to engine mis-alignment. In a few instances it actually originated at the factory where they did not do a good job when commissioning the boats but it is an issue that needs to be checked on every boat periodically in any case.

Engine out of alignment will cause vibration but this is often hidden by the flexible shaft couplings that are installed on all PDQ power cats. The flexible coupling can be both a good thing and a bad thing. On the good side, it does make the boat run smoother and quieter, but on the bad side "hiding" the vibration prevents the operator from knowing that he/she has a problem. If there is vibration, it can lead to premature failure of the dripless shaft seal and the cutlass bearing.

In every case where we saw a leaking shaft seal it was traced to engine out of alignment.

In extreme cases, an out of alignment condition can lead to a "wobble" in the shaft so this also must be checked if a problem has been detected. This "wobble" condition is facilitated by the fact that the shaft length between shaft coupling and aft cutlass bearing is at the maximum recommended distance. This is normally not an issue, but if the engine has been out of alignment for a long period, a "wobble" can easily be created.

What have we learned from all this ? Well, certainly that engine alignment should be checked periodically by a qualified mechanic, one that is skilled in the "art" of alignment. We have also learned that if your shaft seal is leaking or your cutlass bearing is worn, it most likely is caused by an out of alignment condition……but…if the cutlass bearing is really worn, this too by itself, can cause the vibration that then causes the shaft seal to leak.

As noted in an earlier posting there is an upgrade to the boat that has been designed by the boatyard in Stuart that does most of the work on the PDQ's, Stuart Yacht Builders. They have designed a Mid shaft bearing that is installed in the fiberglass shaft tube just aft of where the dripless shaft seal attaches to the tube. This additional bearing allows the shaft to be held straight between the two cutlass bearings and thus a better engine alignment can be achieved. Further, it does eliminate the possibility of a shaft "wobble" entering into the equation. The installation process includes checking the shaft straightness, checking the aft cutlass bearing, installing a new dripless shaft seal, and doing a very exacting engine alignment. In total this is a rather expensive upgrade and one that is definitely not required to have a well running boat. At present there are a few boats that have had this upgrade installed and all of satisfied with the outcome, myself included. I must add that in the case of our boat HERON, we did not have a problem of any kind as I was very consciences about engine alignment, but rather just wanted to "test" this upgrade so I could comment on it with some experience.

Hope this helps clarify this subject.


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