[Sentoa] Overheating or not? Impeller bits

Fri Aug 8 21:16:44 EDT 2008

Impeller bits. 

I found the same thing. My whole set of impeller bits ended up at the intake side of the pump, not the output as you might expect.

Al McKenney
aem2 at prodigy.net
  ----- Original Message ----- 
  From: Cook, Carey 
  To: South East Nordic Tugs Owners' Association (SENTOA) 
  Sent: Friday, August 08, 2008 3:18 PM
  Subject: Re: [Sentoa] Overheating or not?

  I'll add my experience re impellers, even though you indicate that you have checked yours.  Last season I trashed my impeller running slowly around the harbor warming up the oil for an end-of-season oil change.  Early this season I had the Cummins tech out to check out the cooling system.  He checked downstream of the pump and found a few impeller giblets at the oil cooler inlet.  He said that anything smaller would pass through the system.  This season I was running warmer than normal at low cruise (1800 RPMs, 190 degrees), and at normal cruise (2000 RPMs) I was making steam and then temperature approached 200 degrees.  I joined BoatDiesel.com, and in five minutes, I was told to check out the input side to the pump and sure enough, I found the rest of the impeller.  As an engineer it just seemed so logical that the impeller parts would be forced farther into the cooling system, that I couldn't accept any other solution.  At low cruise speed I had enough cooling water for the engine and the exhaust, but at high cruising speed in inlet side of the pump clogged up w/ impeller parts.  It's easy to take off the hose between the sea strainer and the pump.  Then probe the pump inlet with your fingers to see if anything is jammed up in there.  You might be surprised.

  Carey Cook
  32-138 -- LeeLoo
  Racine, WI (berth)

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  From: sentoa-bounces at lists.samurai.com [mailto:sentoa-bounces at lists.samurai.com] On Behalf Of camrpm163 at aol.com
  Sent: Friday, August 08, 2008 2:00 PM
  To: sentoa at lists.samurai.com
  Subject: Re: [Sentoa] Overheating or not?

  Hi Jack, when you replaced the impeller were there any missing vanes? if so they might have gotten caught in the oil cooler or heat exchanger which would restrict flow and cause excessive heat. When an impeller fails you have to retrieve all the little pieces,( which I have had fall backwards and go towards the strainer,I was glad they didn't go the flow way). If you have good flow out the back than check every thing else. You should be able to touch with your hand just about every where water flows but shoot it first with the heat sensor gun. My engine runs around 190 degrees while under way any where from 1400 up to 2400 RPMs & full throttle a little warmer, 200 degrees or more is too hot.
  Good luck
  Richard Maresca
  CARISMA 32-144
  Whitestone,NY

  -----Original Message-----
  From: AJLYNN at aol.com
  To: sentoa at lists.samurai.com
  Sent: Thu, 7 Aug 2008 4:14 pm
  Subject: [Sentoa] Overheating or not?

  Recently, my boat started overheating.  Everybody's best guess was that the problem was probably the impeller. That's been taken care of. I also cleaned the sensor contacts.

  Today, the first time I've had a chance to take her out, she appeared to overheat when running for a relatively short time at 2400 rpm.  She didn't overheat at 2000 rpm.

  I kept trying to test the accuracy of the alarms with a heat sensor gun.  Unfortunately, the overheating occurred on my way back in as an under sail trimaran was crossing and then, again, when I was in the lee of a working tug.  If I pointed the gun at the right places, while trying to avoid a collision at sea, it may be that the gauge is off.  I wonder would that also trigger the alarm since they both react to the same sensor? Could the sensor be off?  

  I've read on this net, I believe, that VDO gauges are usually inaccurate.

  My plan is to change the gauge, as well as have a diver check for barnacles, bags and beards. Before I start worrying about the heat exchanger.

  Usually, this boat will exceed 2400 rpm. Today she didn't.

  As always, all suggestions are welcome.  Also, any thoughts on the maker of the best gauges will help select a replacement.

  Thanks, 

  Jack

  Jack Lynn
  Bunny's Heron
  Nordic Tug 32-102
  Anchorage Marina
  Canton, Ballimur Harbor, Hon!
  on the 
  Patapsco River

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