[C320-list] Prop shakes

[Dave Moores]

Thanks Peter, the boat(and prop) are now 11 years old and I notice a fair
amount of "slop" in the fore and aft direction when I move the blades around
with the boat out of the water. I also had a new cutlass-bearing installed a
while back, which appears to have hard-rubber flutes as the bearing surface,
and I wonder if that is allowing the prop to shake the shaft around more
than a solid bearing would do?

As I mentioned, the problem only occurs when I am at below 2000 revs.
Everyting smooths right out, after a few moments of nasty shaking, once I
open the throttle.  This makes me think that the small amount of slop is
allowing enough imbalance to occur with a partly-unfolded prop, eben though
the baldes on the Gori are geared-together to avoid assymetrical unfolding.

But that is just my guess and anybody else's experiences would be welcome. 

Dave M

-----Original Message-----
From: c320-list-bounces at catalina320.com
[mailto:c320-list-bounces at catalina320.com] On Behalf Of Peter Clancy
Sent: October 18, 2007 11:33 AM
To: C320-List
Subject: Re: [C320-list] Prop shakes


I installed a Gori 2-blade folder three years ago on 'AROBAN' and never
experienced vibration problems.

 I understand that Gori props are precisely balanced when manufactured so
it's unlikely the prop itself is the problem. A loose cutlass bearing or a
warped shaft could be the culprit. However, incorrect installation of the
prop is also a common cause. For example, it's critical to 'mate' the
propellor to the shaft by eliminating any out- of- roundness between the two
mating surfaces. This is done with valve grinding compound and by spinning
the prop on the shaft until it turns smoothly. The other step is to assure
the prop is set fully back on the shaft. It's possible for the key to jam in
the keyway as the prop is pushed on to the shaft thus preventing it from
seating firmly. 

Peter Clancy
'AROBAN'  C320  #222 (former owner)
Miami, FL



  ----- Original Message -----  
  From: Pat Moriarty<mailto:patm at psiurethanes.com> 
  To: C320-List<mailto:c320-list at catalina320.com> 
  Sent: Thursday, October 18, 2007 10:15 AM
  Subject: Re: [C320-list] Prop shakes


  Machine what? Mine did it brand new but gets worse at RPM and I had a 
  new cutlass bearing .

  Pt #130

  At 08:55 AM 10/18/2007, you wrote:
  >My Gori two-blade has started shaking and rattling at intermediate
  >engine-speeds.  It smooths out fine once I rev up.
  >
  >My mechanic says he sees this a lot and it "needs machining".
  >
  >Anybody had a similar situation?  Did machining fix it?  Any other
advice?
  >
  >Dave Moores

  Pat Moriarty
  PSI Urethanes Inc
  PH: 800-888-5156  Fax: 512-837-8733
  Please visit our web site at
  www.psiurethanes.com<http://www.psiurethanes.com/>