Stus-List Impeller Damn...

Gary Nylander gnylander at
Sun May 17 16:51:20 EDT 2015

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 annoying...

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 
  To: cnc-list at 
  Cc: Rick Rohwer 
  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> 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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