Stus-List Impeller Damn...

Rick Brass rickbrass at
Mon May 18 18:44:59 EDT 2015



If I'm not mistaken, having the Sen-Dur retrofit makes it a fresh water
cooled engine, not raw water.


Two water pumps, right? The pump on the front of the engine circulates
water/glycol through the engine block and to the heat exchanger, the second
pumps sea water to the heat exchanger and then to the exhaust mixing elbow?


If that is the case, and the impeller blade is from the sea water pump,
there is about a 90% chance the blade is in the heat exchanger.


Rick Brass

Washington, NC




From: CnC-List [mailto:cnc-list-bounces at] On Behalf Of David via
Sent: Sunday, May 17, 2015 6:01 PM
Cc: David
Subject: Re: Stus-List Impeller Damn...


Thanks all.

Checked obvious hose areas.  Nothing. Ran it today on the hard, seemed fine,
Will be launched  tomorrow.  As we are Bermuda bound in June I need to find
that puppy as it will invariably find its way to the worst spot at the worst
time.   My guess its in the after market (Sen-Dur) heat exchanger.

Wish me luck.  

David F. Risch
1981 40-2
(401) 419-4650 (cell)


Date: Sun, 17 May 2015 16:11:49 -0500
To: cnc-list at <mailto:cnc-list at> 
Subject: Re: Stus-List Impeller Damn...
From: cnc-list at <mailto:cnc-list at> 
CC: muckleyj at <mailto:muckleyj at> 

You can use the shop-vac to blow out the system too...or a garden hose.

On May 17, 2015 4:51 PM, "Gary Nylander via CnC-List" <cnc-list at
<mailto:cnc-list at> > wrote:

I agree with the comments which Rick made. I had intermittent cooling
problems on my Yanmar 2QM15 for a number of years - most of the time when it
had been run for a while, then stopped, then started again. The whistle was


I then had more serious problems, and found the impeller had come apart. I
took all the little pieces of the busted impeller and assembled them with
glue and tape to make sure there was nothing still in the engine. OK. With a
new impeller it went back to overheating every so often like it used to do.


I started again - I ran the engine each time I changed anything... After
checking the hoses, strainer, pump, more hoses, and replacing the zincs, I
found not much water coming through the hose leading to the zinc at the
forward part of the engine. Confusing. When I pulled the hose going to the
zinc area and fired the engine, I found a piece of an impeller which was
hard as a rock and coated in rust stuck in there. The impeller I had just
pulled was recent, no rust and not hard. All the other impellers I have
changed in 20+ years of ownership had been whole. 

The only thing I can think of is that piece must have been in there for
years - - - and only caused problems in certain conditions. Once it was
removed, I have had no cooling problems for the last year!


Start at one end, and follow it through. Blow out everything as you go.


Gary Nylander

30-1 Maryland

----- Original Message ----- 

From: Rick Rohwer via CnC-List <mailto:cnc-list at>  

To: cnc-list at <mailto:cnc-list at>  

Cc: Rick Rohwer <mailto:rickrohwer at>  

Sent: Sunday, May 17, 2015 12:44 PM

Subject: Re: Stus-List Impeller Damn...


Hi David, 

i'll chime in and hope it helps. 


If you are lucky, the vane was torn to tiny particles and pushed all the way
through the cooling system and you are free as rain!


If you are like me, it is lurking somewhere in the system between the pump
and the exhaust outlet and pretty much the same size as when it left.  In a
raw water cooled application, that means it could be anywhere in the cooling
system of your engine block, potentially blocking or contributing to future
blockage.  In a fresh water cooling system I think the chunks end up in the
heat exchanger or where the raw water is introduced to the exhaust gases.


Just as a suggestion, try not to run the engine, and starting at the pump,
work your way up line carefully checking for pieces in the hoses hoping that
it lodged in that line prior to entering the block.  Hang on to any chunks
you find so you can get an idea of how pulverized it is.  After that point i
doubt that there is much chance you would find it.  i don't know that there
is much you can do after that except watch temps and signs of overheating.
Maybe the new fully functioning impeller will push it out over time.  


I like to "lay hands" on my diesel occasionally!  I had a hot tub that would
heal itself on occasion after a brief group hug!  


Good luck,



C&C 37+ Paikea

Poulsbo, WA




On May 17, 2015, at 6:01 AM, David via CnC-List <cnc-list at
<mailto:cnc-list at> > wrote:


A first time.  Found a missing impeller vane on my 3QM30.  The whole damn
vane.   Suggestions before I start tearing the who damned cooling system
apart?   Its a raw water cooled engine with a Sen-Dur retro-fit.

Thanks in advance.

David F. Risch
C & C 40-2
(401) 419-4650 (cell)


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