Temp Gauge Acting Strange

Discussion in 'General Maintenance/Repair Questions' started by Boater420, Mar 1, 2018.

  1. Boater420

    Boater420 Well-Known Member

    Mar 11, 2015
    Clearwater, FL
    '97 330 Sundancer
    V-Drives
    Westerbeke 4.5BCG
    Twin Merc 454's
    I was out on the water last weekend and noticed my port temp gauge acting weird.

    Started out fine, warmed up to 170 degrees, idled around for a while and all was good. Then rather abruptly, the gauge went to all the way to cold...slowly climbed back to 170 and repeated the process over and over.

    It never climbed past 170, the raw water was warm coming out the exhaust, there was no signs of overheating. Everything was fine except the way the gauge was operating.

    New bravo pump housing and impeller, circulating pump, thermostat and risers & manifolds last year. It's been acting fine otherwise.

    Any ideas? Temp sending units? Gauge?
     
  2. JimG

    JimG Well-Known Member SILVER Sponsor

    Nov 4, 2008
    Southern WV
    2007 310 DA
    Kohler 5ECD
    Twin 350 Mags
    Raw Water Cooled
    V-Drives
    Sounds like a connection issue either at the sensor or the gauge... corroded or loose ground maybe.
     
  3. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor

    Apr 21, 2009
    PA
    Various
    Various
    Switch the wires on your gauges stbd for port and see if the problem follows the wires (or switch the gauges as that might be easier). Since the needle moved "abruptly" it sounds more like an electrical issue than a real issue.

    Also check for dirty/loose connectors at the engine and gauge side.

    Since it kept repeating itself, though, I'd lean towards a failing temp sender.
     
  4. Boater420

    Boater420 Well-Known Member

    Mar 11, 2015
    Clearwater, FL
    '97 330 Sundancer
    V-Drives
    Westerbeke 4.5BCG
    Twin Merc 454's
    I see two wires at the thermostat housing which look like sender wires. Are these both for the sender or is one for the system monitor?
     
  5. CliffA

    CliffA Well-Known Member GOLD Sponsor

    Dec 29, 2009
    Lake Norman, NC
    2001 Sea Ray 340DA
    Name: 'Happy Place'
    4.5kW West. Generator
    Purchased Nov. 2014
    Fresh Water Use
    Twin Merc. 6.2L (MPI)
    Raw Water Cooled
    V-Drive Transmissions
    one wire should be for the temp gauge and the other supplies the coolant temp to the engine ECM......

    cliff
     
  6. Boater420

    Boater420 Well-Known Member

    Mar 11, 2015
    Clearwater, FL
    '97 330 Sundancer
    V-Drives
    Westerbeke 4.5BCG
    Twin Merc 454's
    Are the senders for each the same? Is there a way to tell which one is the temp gauge?
     
  7. Espos4

    Espos4 Active Member

    471
    Jan 1, 2017
    Long Island NY
    2007 240 Sundeck
    350 MAG Bravo 3 W/DTS
    For a 1 wire sensor:
    Unplug one with the engine running. The temp gauge should go to cold. Ground that same wire and the temp gauge should go to hot.

    For a 2 wire connector, temporarily shorting the 2 wires together should send the gauge to Hot.
     
  8. Boater420

    Boater420 Well-Known Member

    Mar 11, 2015
    Clearwater, FL
    '97 330 Sundancer
    V-Drives
    Westerbeke 4.5BCG
    Twin Merc 454's
    Thank you guys, I'll be testing this weekend and post what happened.
     
  9. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor

    Apr 21, 2009
    PA
    Various
    Various
    "Typically"... the ALL tan wire will feed your gauge. The Tan w/Blue wire will be the overtemp alarm.
     
  10. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor

    Apr 21, 2009
    PA
    Various
    Various
    Oh, you can also switch the senders and see if the issue swaps to the other gauge.
     

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