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Is closed cooling system the same as freshwater cooling system?

Discussion in 'General Maintenance/Repair Questions' started by Captain Jimbo, Nov 21, 2020.

  1. Captain Jimbo

    Captain Jimbo Member

    May 10, 2012
    1997 Sundancer 250
    Mercruiser 5.7L Bravo
    I have a new MerCruiser Plus 357 bravo 4V engine on my boat and they installed a closed cooling system with heat exchanger. My question is is that the same thing as a freshwater cooling system?
  2. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    "closed" is a better term. "raw water"is sometimes used with an open system
    Captain Jimbo and Creekwood like this.
  3. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor GOLD Sponsor

    Apr 21, 2009
    Generally speaking, yes. Although "freshwater cooling" is really an incorrect term to use since antifreeze is being used in the engine, not water. But, yes. The better terms are "closed" and "open".
    Captain Jimbo likes this.
  4. Henry Boyd

    Henry Boyd Well-Known Member GOLD Sponsor

    Apr 24, 2007
    Newburyport, on the peaceful and serene Merrimack
    ‘09 Sabre 38 Hardtop Express “Serenity”
    Volvo D6 w/IPS450 Pods
    And to furthure confuse the story, both closed and raw water cooling use the water the boat is floating in for cooling. The closed cooling engines use ocean/lake/pond/river/stream (OLPRS) water to cool not only the heat exchanger, but also to cool exhaust and intake (?) manifolds. The raw water cooled boats use OLPRS for everything.

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