vibration

[David]

Hello,
 
 Over the winter I had the boatyard change my mounts to the vetus k50's, change to a stainless shaft, change the stuffing box and change the cutless bearing.
 
 Currently, in neutral the engine sounds GREAT at all rpm's.  In forward, above 1450 rpm's the engine has a harmonic/vibration that will not go away as I raise the rpm's to a max of 2600 rpm's.  Below 1400 rpm's the engine sounds and feels GREAT also.
 
 When I put my hand on the stuffing box above 1450 rpm's I feel the same vibration/harmonic that I hear in the cockpit while engining.
 
 Any thoughts/suggestions?

[HydroTherapy]

I wrote the above question for help and did not show up as a registered user??? :confused:

[HydroTherapy]

Ron: The stuffing box was original and the boatyard told me it should be changed.  The shaft is new and stainless steel.
 
 The boatyard seems to do good work, but with this kind of job it do not know.  Is it possible the vibration I feel in the stuffing box is coming from the hull and going to the shaft/stuffing box?
 
 Thanks for the input, when I call the boatyard I will be able to give them more information.
 
  :)David

[Jeff Tancock]

I agree with Ron, but don't forget to check the engine coupling/ shaft alignment. I just switched mounts this past winter and noticed a shake before I had the alignment right on.

[HydroTherapy]

Jeff, The engine coupling/shaft was aligned before the boat was put in the water and adjusted once it was in for over 24 hours.  Is there a chance that the vibration is going from the hull to the shaft at the higher RPMs?
 
 Thanks, David

[Jeff Tancock]

David,
 We can't tell you what is wrong. If everything is fine in neutral but not when in gear then it probably has something to do with the shaft turning or the engine being under load. You could have a problem with the prop., the shaft, the alignment or maybe even the lag bolts or nuts for the mounts not being tight. Something's not right and you'll just have to go through it all step by step. With my new mounts and the improved shaft centering and alignment there is no vibration at any time. Good luck!

[jrupinsk]

Could you have a loose shaft zinc?
 I changed the position of mine this
 year and installed it closer to the
 strut, and noticed less vibration.
 
 Just a thought
 
 Jan & Liz Rupinski
 s/v La Vie Dansante
 C34mkII #1311
 r/v Southwind 35S "Moose"
 Cape May, NJ

[John Gardner]

I did the same thing myself this winter, except that I re-used the bronze shaft.  I pulled and replaced the shaft past the rudder, and due to the stress and bending felt very uncomfortable doing it.  However, the result was a quieter installation throughout the rpm range, so I presume no harm was done.  And I know many other C34 owners have done it this way, but I wonder if your yard did the same and whether it could have caused any lasting effect?  The fact that it is quiet at some rpm, but not at others suggests to my inexperienced mind that there is something out of balance rather than mis-aligned.  In that case could the prop have been damaged during removal.  As suggested above, I put my zinc close (about 2 inches I think)to the strut, and BTW, the prop should only have 1/2 inch or so between the hub and the cutless bearing.  (On the other hand presumably these two are not too close - the shaft moves slightly forwards or backwards depending on transmission selection - this unlikely possibility would be ruled out if the vibration is there in both directions.)
 Maybe you could get the yard to listen and comment.  They ought to take some responsibility, even if it is no more than an opinion.
 Good luck.

[HydroTherapy]

John,  Thanks for info...I moved my boat to Stamford CT, from Bridgeport and the boatyard has not returned my two calls.  I will keep at it.
 
 Thanks,
 David

[Denny #142 Turning Point]

David,
    Uncouple your shaft flange from the transmission by removing the four bolts.  Slide the shaft and flange back about an inch.  Move the shaft to its full verticle (up and down) travel.  Next move the shaft to its full horizontial (left and right) travel.  These distances should be about a half inch or so.  Once you have the approximate center of the verticle and horizontial movement, put a block of wood or whatever under the shaft to not allow it to return to its gravity position.  Now move the engine mounts to match the flange coupling.  Once you have the engine so the flange slides into the transmission easily use the feeler gauge to refine the allignment to .oo3.  My yard always alligned in the gravity position and I always had a harmonic vibration.  Since I have followed this method on my own, bliss.  Good luck.
 Denny #142 Turning Point

[HydroTherapy]

Thanks Denny,
 
 I am pretty handy, but I think this is over my head.  The engine was aligned twice.  I do not want to make a bigger mess of this by doing it myself for the first time.  Is there a way to confirm that the harmonics is coming from the engine/shaft/prop/etc?  I am confused...I did feel the harmonic on the stuffing box, but I just want to be sure...Some people tell me it could be going from the hull to the shaft???  :confused:
 
 Thanks for the insight and any new ideas,
 
 David

[Ray Erps #923]

Howdy,
 
 Looks like you've got some pretty good advice.  I don't think you can rule out missalignment of the prop shaft because you can feel the vibration at the stuffing box, as any vibration from the prop shaft would transmit thru the stuffing box into the rest of the hull.  By just backing out the coupling bolts a bit and using that .003 feeler guage already mentioned, you could check the boat yards work without too much effort.

[SteveLyle]

Vibration being transmitted from the hull to the shaft?  What would be the source of the vibration?  The only source I can think of would be the engine, in which case you should be able to see it and feel it through the hull.  And transfer of vibration from the hull to the shaft would require either shaft/hull contact, or VERY close proximity, meaning that your shaft isn't centered in the log.
 
 Denny describes what you need to do.  I'd bet you're capable of doing it.  I'd also bet that you care more about how well it gets done than the yard.  There have been numerous stories re: vibration (and other maladies) where owners have paid yards lots of bucks over several YEARS to resolve the problem, to no avail.  When the owners did their own research (like you're doing) and took their own action, they were able to isolate and fix the problem.
 
 Centering the shaft and aligning the shaft/engine is pretty basic.  I don't see any way you could cause any permanent damage by trying it - the worst that could happen is that you decide it's not worth your trouble (after banging your head a few times on the aft cabin ceiling), so you call the yard back in to finish it.
 
 Good luck, let us know how this ends up.

[Aquakon]

I've read this thread twice now and...
 has the prop itself been checked for
 fouling?  If I remember correctly, a decent-
 sized wrap of seaweed would cause approximately
 the same symptom set, n'est-ce pas?
 
 Rumours of my Death Persist

[Denny]

David
     All I can share with you is my experience on my boat, but I threw a bunch of money at a new SS shaft, balanced the prop, new shaft bearing, drivesaver which made it worse.  Ultimately I ditched the drivesaver, got new engine mounts which a yard helped install on half inch starboard because the new mounts were a little shorter.  The yard had a small portable jack for lifting the engine.  I confess a yard in FL showed me the alignment technique.  I have since pulled the engine to have a rear main seal repaired and reinstalled it myself using the technique I described for alignment.  My engine runs like a sewing machine now and before, the tapping noise and harmonic vibration was so loud I had to wear foam ear plugs to drive.  We have lived aboard for 2 yrs now and put 2000 hrs on the engine.  
 Good luck,
 Denny
 
 Denny