[C320-list] Vibration under power issue

[Graeme Clark]

Just to add to Chris’s comments. I gave up in frustration with my shaft alignment attempts and when I gave the job to the yard and watched, I realised what I was doing wrong, which is sort of obvious unless it isn't obvious to you - as it wasn't to me! it is this:-

The very first thing you need to do is make sure the prop shaft is centred in the stern tube!

If you don't do that then although you can move the engine on its mounts to get the shaft couplings aligned, the shaft will not be running true through the cutless bearing!

Hope that helps

Graeme, 366, Jaskar

On 27 Jul 2016, at 20:52, Chris Burti <clburti at gmail.com> wrote:

> Alignment can be a bit trickier than many yards realise.
> The first rule is that it has to be done with the boat in the water and at
> least couple of days after being put back in the water so that the hull has
> had a  to settle back into its normal shape.
> 
> Second rule is that the alignment has to be done four times with the
> coupling faces sequentially rotated at 90 degree intervals to be assured
> the the couplings are installed perfectly square on their respective
> shafts. If they are not (and that is not uncommon), you can't truly align
> the shafts and you will not be successful in getting vibration reduced to a
> minimum.
> 
> Squaring the couplings on either of the shafts, if required, is a job for a
> machine shop requiring a haulout.
> 
> CB
> Commitment, #867
> 
> Chris Burti
> Farmville, NC
> 
> 
> On Wed, Jul 27, 2016 at 3:36 PM, MSail <msail at baymoon.com> wrote:
> 
>> I'd appreciate any feedback from the fleet regarding a vibration issue
>> that arises above about 2000 engine rpm.
>> 
>> 1996 C320
>> Westerbeke 30B
>> JS Transmission
>> 16" Max Prop (3-1/4" clearance tip to hull)
>> 
>> Problem:  In gear, vibration/rattle above 2000 rpm, increasing further as
>> engine speed increases to maximum.    Engine and transmission moving
>> considerably on mounts when vibration is encountered. In neutral, engine
>> runs smoothly to max rpm, no vibration.
>> 
>> I've replaced:
>> 
>> Engine mounts (with Westerbeke OEM original types)
>> Prop shaft (from original bronze to Aquamet 22)
>> Cutlass bearing (replaced 2 years ago, showing some wear as of 7/16 but
>> not deemed excessive)
>> Done careful shaft-transmission coupler alignment with yard.
>> 
>> Have NOT replaced damper plate.
>> 
>> Thanks in advance for comments.  Has anyone else on this list experienced
>> this problem with this setup?
>> 
>> Michael  Mellon
>> Santa Cruz, CA
>> msail at baymoon.com
>> 

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