Sizing a new oil cooler

Discussion in 'Gas Engines' started by 7228sedan, Jun 20, 2018.

  1. 7228sedan
    Joined: Nov 2009
    Posts: 320
    Likes: 7, Points: 18, Legacy Rep: 60
    Location: New Jersey USA

    7228sedan Senior Member

    Looking to replace my oil cooler with my repower project. I'm installing a fresh 454 with all stock Mercruier 340 components. The cooler I had was a stern drive unit with half of the body taken up as an unused power steering cooler. My tandem cooler now is about 4-5 inches on each side. My biggest concern is, can I go too big? I am looking at an 8 inch unit (5 inch body) as well as a 12 inch (9 inch body). Need I be concerned with too much cooling capacity by upgrading to the 12 inch unit?
     
  2. gonzo
    Joined: Aug 2002
    Posts: 13,539
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    Location: Milwaukee, WI

    gonzo Senior Member

    Oil that runs too cold will build up sludge. It should get hot enough to boil moisture off.
     
  3. 7228sedan
    Joined: Nov 2009
    Posts: 320
    Likes: 7, Points: 18, Legacy Rep: 60
    Location: New Jersey USA

    7228sedan Senior Member

    Exactly... hence my concern. I have a feeling that some of my oil pressure issues at higher RPM's were due to the oil getting too hot. Unfortunately it's just a guess as I don't have an oil temp gauge. The old motor had so much blow by that it would blow the dipstick out of the tube at anything over 3600 RPM's. I am guessing that the excessive blow by was potentially contributing to the oil temp? then again, as I don't have an oil temp gauge it's all speculation.
     
  4. gonzo
    Joined: Aug 2002
    Posts: 13,539
    Likes: 369, Points: 93, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    Blow-by will heat up the crankcase. I assume the cooler doesn't have a thermostat.
     

  5. 7228sedan
    Joined: Nov 2009
    Posts: 320
    Likes: 7, Points: 18, Legacy Rep: 60
    Location: New Jersey USA

    7228sedan Senior Member

    no thermostat that I'm aware of unless it's in the remote filter adapter on the block. It's all factory Mercruiser components for a 1990 Bravo 454. I ended up ordering a factory spec 8 inch cooler. This cooler was OEM on the straight inboard 7.4 of that vintage. As my motor began life as a Bravo, then was transplanted as an inboard it still had the Bravo spec dual oil/power steering cooler. I was leary on going with the 12 inch cooler as I din't want to over cool the oil. Thanks as always! As soon as I get it in the water I'll report back.
     
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