{Stus-List} Engine vibration and RPM fixed

dwight veinot dwightveinot at hfx.eastlink.ca
Sun Jun 21 05:43:54 EDT 2009


Thanks Chuck

 

My engine has always been quiet and smooth, I changed 2 mounts and adjusted
all 4 when I got the boat but I will check for the selector knob on the back
of the tach.  Typically I drive the engine at 15-1800 and with my prop (3
blade autoprop) that drives the boat at 5-6 kts unless I am going into a
strong headwind and then I rev to about 2400 to achieve 6 kts. The boat will
go faster under power at full engine rev but I seldom do that.  I am willing
to sacrifice speed for quiet as long as I can go along happily at 5-6 kts. 

 

Dwight Veinot

1974 C&C 35, Alianna

Head of St. Margaret's Bay, NS

 

  _____  

From: cnc-list-bounces at cnc-list.com [mailto:cnc-list-bounces at cnc-list.com]
On Behalf Of cscheaffer at comcast.net
Sent: June 21, 2009 12:40 AM
To: cnc-list at cnc-list.com
Subject: {Stus-List} Engine vibration and RPM fixed

 


Dwight,

I thought you might want to know, I measured the actual RPM of my Universal
M4-30 using a hand held dial tachometer and discovered the cockpit tach was
reading low.  For years, my engine seemed to enjoy running at 1800 to 2200
RPM and achieved hullspeed easily at those rpms.  Experts were convinced I
had the wrong prop and had me worried I was hurting the engine running it at
those low RPMs.  The handheld tachometer showed me that the engine was
actually turning between 3000 and 3400.  I changed a selector knob on the
back of the cockpit tach to "15" and it still doesn't read exact, but reads
into the 3000's now.  

 

Also, I found a fix for the noise and vibration whenever the engine ran.  I
bought new mounts but don't have to install them.   It was eliminated by
moving the exhaust hose.  The hose had become jambed against a bulkhead
where it bends underneath and this caused vibration throughout the boat.  I
was able to pull the whole hose and muffler closer toward the engine, by
simply undoing clamps and sliding it all forward to provide more slack and a
bigger radius bend where it exits the engine box.  It was that way when I
bought the boat but has gotten worse.  

 

Amazing difference.  It's as quiet as a Yanmar on a new boat now.  Launched
Friday, tuned the rig today and hope to sail between showers tomorrow.

 

Chuck

1990 C&C 34R

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