Stus-List Overheating due to plugged knuckle

Don Jonsson dbjonsson at
Mon May 13 13:52:03 EDT 2013

Once, many years ago.  I checked it when it overheated two years ago and it
was fine - i.e. the bit didn't come off of it.  I didn't check it this time,
as when I cleared the knuckle the water was pumping fine and I was running
late in catching the ebb home.

-----Original Message-----
From: David Risch [mailto:davidrisch75 at] 
Sent: May-13-13 10:47 AM
To: Don Jonsson ; cnc-list at 
Subject: Re: Stus-List Overheating due to plugged knuckle


Ever blow an impeller in years past?
                                                      David F. Risch
(401) 419-4650 cell

-----Original Message-----
From: Don Jonsson <dbjonsson at>
Date: Mon, 13 May 2013 17:44:51 
To: <cnc-list at>
Subject: Stus-List Overheating due to plugged knuckle

Hello all
I have an elderly Yanmar 3GMD engine that is raw water cooled.  It has
plugged twice in the last two years where the water goes through a knuckle
into the mixing elbow.  The first time (summer before last) was some solid
bit that had gotten stuck - how it got there I don't know.  The last time
(last week) was due to a tar like substance gumming up the knuckle.  Easy to
clear and I was on my way, but is this a harbinger of something more
I took the mixing elbow off a few years back and cleaned it, guess it is
time to do that again.  
Is the plugging coming from the exhaust and working its way into the knuckle
- for example unburned diesel?
Thanks for any insight.

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