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Engine Temp difference after coming down from cruise

Discussion in 'Technical Discussion' started by CSkipR, Dec 19, 2017.

  1. CSkipR

    CSkipR Member

    Joined:
    Aug 16, 2008
    Messages:
    832
    Location:
    New Smyrna Beach, Fl
    Both Man CR900 engines run the same temperature 190-192 at cruise 1800-1950 rpm. I had the thermostats (3 on each engine) replaced about a year ago and since then each engine has a different temp reading after coming down from cruise to idle. The starboard engine will read about 9 degrees cooler than the port. I believe the issue is with the starboard engine. The port when coming down to idle from cruise will read 187-189f and the starboard 178. I´m guessing one of the thermostats is either a different temp setting or is possibly sticking. Any ideas.
    I'm not overly concerned with the temp difference but would like to get both engines close to the same.
  2. Lepke

    Lepke Member

    Joined:
    Dec 26, 2015
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    66
    Location:
    US West Coast. Cruise NW Passage to Alaska.
    Mass produced items like thermostats often have slight differences. Not only temperature but can have flaws like sticking open. The only real way to know is to remove the thermostats and test them in water and note the differences. I've had new thermostats not completely close and others stick wide open.
    I do my own engine work and usually test them before installing. You'd think for the price of diesel OEM thermostats, they'd all be perfect.
  3. Capt J

    Capt J Senior Member

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    Jul 11, 2005
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    9,812
    Location:
    Fort Lauderdale
    You need to photo temp both engines at the temperature sender to really verify TEMP. I would guess it will most likely be your temperature gauge sender.
  4. CSkipR

    CSkipR Member

    Joined:
    Aug 16, 2008
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    Location:
    New Smyrna Beach, Fl
    You got that right. $1500 for the 6 thermostats.

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