140 thermostat?

Discussion in 'General Maintenance/Repair Questions' started by Happy Dayz, Feb 2, 2018.

  1. Happy Dayz

    Happy Dayz Active Member

    359
    Jun 26, 2017
    Sarasota, FL
    '06 260 Sundancer, 6.2, BIII, Kohler 5kw
    79' classic Kona Family Cruiser jet boat..
    6.2 w/ BIII, 502 w/ Berkekley
    So on another forum I was told for raw water cooling I should be running a 140 thermostat not the 160 that is in it and on the parts list..

    6.2L Bravo III

    What does CSR say?... Thanks in advance
     
  2. BillK2632

    BillK2632 Well-Known Member SILVER Sponsor

    Jun 25, 2009
    Lake Norman, NC
    1999 185 Bowrider,
    Mercruiser 4.3, Alpha I
    All of my boats have been rawater cooled in freshwater, all have had the 160* thermostat - that translates to a running temp of 170-175*. I think 160* thermostat is pretty much the standard for marine engines these days, but there are some camps that say in salt water you should run the cooler 140* thermostat - something about saltwater and salt deposits at the higher temperatures.
     
  3. Siboatguy

    Siboatguy Active Member GOLD Sponsor

    230
    Mar 28, 2016
    Holmdel,NJ
    2005 Sea Ray 320 Sundancer
    Twins V-Drives
    2017 5.7 Mercruisers
    I also like the 140s.... It runs around 150 to 155 when warm and its a nice temp...
     
    Happy Dayz likes this.
  4. Happy Dayz

    Happy Dayz Active Member

    359
    Jun 26, 2017
    Sarasota, FL
    '06 260 Sundancer, 6.2, BIII, Kohler 5kw
    79' classic Kona Family Cruiser jet boat..
    6.2 w/ BIII, 502 w/ Berkekley
    giving her a run today so will see... stoked to get on the water!
     
  5. northern

    northern Well-Known Member

    Jan 17, 2007
    West coast Vancouver to Alaska
    380 Aft Cabin 1989 GPS and Charts by Nobeltec
    Twin 454 strait shaft
    We have fresh water cooling (anti freeze) and 140 thermostats I was told they were used to help stop salt deposit. Engines run 160 F measured with heat gun at the thermostats.
     
  6. JVM225

    JVM225 Well-Known Member

    Apr 8, 2008
    Farmingdale, NY
    2002 410 Sundancer, Monaco Edition.
    3126 Cats.
    I’m pretty sure thenrawmwater T stats are supposed to be 140 and the fresh water 160.
    My old 300 was raw water cooled and I used 140’s.
    When I repowered I installed FWC on the new motors and used 160’s.
     
  7. Happy Dayz

    Happy Dayz Active Member

    359
    Jun 26, 2017
    Sarasota, FL
    '06 260 Sundancer, 6.2, BIII, Kohler 5kw
    79' classic Kona Family Cruiser jet boat..
    6.2 w/ BIII, 502 w/ Berkekley
    update:

    140 thermo... not long pulling out temp up to 150's, up on plane, holding 158, then started to tick up.. 171... on another run back in about 30 min in was up to 176.... spikes to 180s coming off plane.. cools back down to 165...

    seems just doesnt get enough water... UUUGGGGGG

    when back flushing from raw pump out through outdrive water flows freely..

    going to do barnacle buster...
     
  8. 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
    you could just run the engine without a t'stat temporarily.....if it still runs hot then the problem is definitely not anything to do with a t'stat.....but I think you have already proven that....

    cliff
     
  9. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor

    Apr 21, 2009
    PA
    Various
    Various
    I think it was in one of your other threads about this, but we talked about the 140* t-stat as being a "band-aid", not a solution? Lowering the t-stat is not a solution to an overheating engine. When you say "water flows freely", that doesn't tell/show how MUCH water. I think we discussed this, as well... doing the water pump test. Have you done that, yet? I don't recall if you had checked the manifolds and risers, as well?

    Your other post was the one with the scored impeller housing, right?
     
  10. Espos4

    Espos4 Active Member

    509
    Jan 1, 2017
    Long Island NY
    2007 240 Sundeck
    350 MAG Bravo 3 W/DTS
    What about the water pressure readings, is it still low?
     
  11. Happy Dayz

    Happy Dayz Active Member

    359
    Jun 26, 2017
    Sarasota, FL
    '06 260 Sundancer, 6.2, BIII, Kohler 5kw
    79' classic Kona Family Cruiser jet boat..
    6.2 w/ BIII, 502 w/ Berkekley
    manifolds, risers and elbows newer and cleaned out..

    the scoring on the pump is nominal relative to the challenge, imho

    the 140 was another test and specific question but relative to the overheating...

    4k rpm...5.6 psi

    also going to do the pump test...
     
  12. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor

    Apr 21, 2009
    PA
    Various
    Various
    Happy, I got your PM. In response to your question about the intake hose... Actually since you likely have the 3-point drain system, you can either grab the hose from the input side of the water distribution housing or the power steering cooler.
     
    Happy Dayz likes this.

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