[C320-list] New shaft

[Jeff Hare]

There's a difference between it shaking at low idle which they do (just look at it when idling!), and a rather harsh brief shudder that happens when powering down quickly.

The former is in the design.  The latter will certainly provide you with a need to put on new engine mounts more frequently.  It is most likely because you're powering down to an idle that is too low for your particular engine.  850-875 is about the minimum by spec., but it's a guideline not a specific number.    

Keep in mind that even though our engine *idled* very nicely at 860 (which is where it was before my adjustment) it went through a terrible shudder when it reached that RPM on powering down fast, after that it idled nicely again.

Ours is currently around 890-ish rpm and you can now power it down as fast as you like with no shudder.  Going into and out of gear is still very smooth.

So... Don't live with it.  Fix it!  Takes 5 minutes tops.

-Jeff

-----Original Message-----
From: C320-list [mailto:c320-list-bounces at lists.catalina320.com] On Behalf Of Gene Helfman
Sent: Tuesday, June 17, 2014 5:38 PM
To: C320-List at catalina320.com
Subject: Re: [C320-list] New shaft

Our mechanic on #398 (1997) says the Yamaha 3GM30F is called a "shaker" at low rpm, i.e., it's in the design.  He's worked on every type of diesel from a few hp to several thousand and knows his stuff.  Take home: live with it I guess.


On Tue, Jun 17, 2014 at 2:34 PM, christopher Brearley <cjbrearley at gmail.com>
wrote:

> Hi Jerry,
>
> I have recently replaced my engine mounts with genuine Yanmah product 
> and there is still the vibration when reducing RPM. Cutless bearing is 
> also fine, so I am unsure of what is causing it. Reduce RPM slowly?
>
> Chris,
>
> WeaRitz@
> #374
>
>
> On 17/06/2014, at 10:19 PM, jsheets at aol.com wrote:
>
> > Thanks all for the responses/advice. I suspect I will be adding 
> > motor
> mounts to my project list.
> >
> > Jerry
> > JellyRoll  #890
> >
> >> On Jun 16, 2014, at 5:35 PM, Jim Brown <jbrown5093 at gmail.com> wrote:
> >>
> >> You can check if the vibration is in the motor mounts pretty easily.
> >> Uncover the engine and (watch out for the belts and pulleys) put a
> longish
> >> pry bar or big screw driver in the motor mount. Pull up hard. 
> >> You'll be surprised about how much they raise up. With the motor 
> >> mount stressed throttle up and if it is a mount the vibration 
> >> should be gone or much better. Do each mount individually. Mine 
> >> (2004) are very weak and when throttling down to idle it sounds 
> >> like a bucket of bolts just above idle speed when there is 
> >> significant vibration. With the mounts stressed-no noise at all. 
> >> Getting ready to replace them . I believe that yanmar recommends replacement every 4-5 years (I suspect nobody does that).
> >>
> >> Jim Brown
> >>
> >>
> >>> On Mon, Jun 16, 2014 at 4:35 PM, <jsheets at aol.com> wrote:
> >>>
> >>> Probably around 800 - 1000.
> >>>
> >>> Jerry
> >>>
> >>>> On Jun 16, 2014, at 3:11 PM, <tharrison at innovations-plus.com> wrote:
> >>>>
> >>>> Just wondering what is you starting RPM"s
> >>>>
> >>>> Ted - hull 424
> >>>>
> >>>> -----Original Message-----
> >>>> From: C320-list [mailto:c320-list-bounces at lists.catalina320.com] 
> >>>> On
> >>> Behalf
> >>>> Of Andrew Santangelo
> >>>> Sent: June-16-14 2:30 PM
> >>>> To: C320-List at Catalina320.com
> >>>> Subject: Re: [C320-list] New shaft
> >>>>
> >>>> Jerry,
> >>>>
> >>>> It could be related tot he cutlass bearing.  I have had this 
> >>>> replaced
> 3
> >>>> times over the last 18 years on Dawn Treader.  I also had a drive
> saver
> >>>> installed for the Autoprop and it saves on wear and tear with the
> engine.
> >>>>
> >>>> Andrew Santangelo
> >>>>
> >>>> C320 "Dawn Treader"
> >>>> #333
> >>>> Holland, MI
> >>>>
> >>>> J22 "Blitzkrieg"
> >>>> Elephant Butte, New Mexico
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>> On Jun 16, 2014, at 2:26 PM, jsheets at aol.com wrote:
> >>>>>
> >>>>> I recently had a new prop shaft installed due to some previous
> problems
> >>>> with the old shaft. Since installed, on two occasions I have had 
> >>>> a
> strong
> >>>> vibration of the shaft and transmission when starting out at low
> speeds.
> >>>> Once given more throttle it works itself out. Does not do it when
> slowing
> >>>> down from higher speed, only in early acceleration. Mechanic is
> convinced
> >>>> the alignment is correct. Says he thinks part of the problem is 
> >>>> the
> motor
> >>>> mounts Yanmar uses, allowing for too much movement of the motor. 
> >>>> Any thoughts or similar experience anyone can share is appreciated.
> >>>>>
> >>>>> Jerry
> >>>>>
> >>>>> JellyRoll  #890
> >>>
>
>


--
Gene Helfman, Professor Emeritus
Odum School of Ecology, University of Georgia PERMANENT address:
    498 Shoreland Dr., Lopez Is., WA 98261
    (360) 468-2136
    genehelfman at gmail.com

"You noticed nobody gives a damn about beached minnows."