8.1L heat exchanger

Discussion in 'General Maintenance/Repair Questions' started by Nmor830, Sep 12, 2019 at 3:37 PM.

  1. Nmor830

    Nmor830 Member

    49
    Sep 12, 2016
    Channel Islands
    2008 340 Sundancer
    8.1l Mercruisers
    Need to replace the heat exchanger on the strb. engine. It leaks around the end cap that pressed into the tube chamber. It’s not the rubber gasket or O ring. Thought of taking it to a radiator shop but not sure they can do the repair.
    On line found an aftermarket one (mr. cool) for half the price of oem. Has anyone used one of these and if so with success? Thought I’d try for some feedback before placing order.
    Thanks,
    Nick
     
  2. Frtbroker

    Frtbroker Active Member

    112
    Feb 12, 2014
    Illinois
    1998 370 Sundancer 10ft dinghy
    7.4 Horizons HO
    I just replaced mine with Mr. Cool............... It was actually pretty easy, and they shipped out same day. great customer service
     
  3. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    If the end cap is warped it can be replaced, if the end of the HE has an irregular surface, it can be machined flat. Machine shop not radiator shop

    If that's the only issue, the leak, this will be a lot cheaper fix.
     
  4. Sublimetime

    Sublimetime Active Member

    673
    Oct 22, 2007
    clifton nj
    420 da
    454
    just putting this out there-- I have two -vintage-2000 mercruiser oem heat exchangers from 7.4 mpi horizon h. o. motors. they are the 1/2 fresh water cooling system. FOR SALE very cheap. They were taken off at 1.5 years old when motor was converted to full fresh cooling. LOOK LIKE NEW> PM me.
     
    joeyleggz likes this.
  5. Jimmy Buoy

    Jimmy Buoy Well-Known Member

    Dec 3, 2008
    Sarnia, Ontario, Canada
    340 Amberjack
    twin 8.1S 370 Hp + 4.5 Westerbeke Genset
    8.1's have specific heat exchangers. They are not like the normal ones that have hoses attached so one from another engine is unlikely to be useable without some major modification.

    Is yours leaking coolant or sea water?
     
  6. Nmor830

    Nmor830 Member

    49
    Sep 12, 2016
    Channel Islands
    2008 340 Sundancer
    8.1l Mercruisers
    I’m not sure? What’s bad it’s leaking directly on to the alternator. There’s green corrosion around the end cap which makes me think it may be sea water.
     
  7. LG111

    LG111 Active Member

    569
    Jan 4, 2015
    NW
    410
    8.1
    I have replaced all coolers and heat exchanges to Mr. Cool on my 8.1S's. Salt water and Zero issues and half the cost. Three years ago.
     
  8. Mike sandor

    Mike sandor Active Member GOLD Sponsor

    135
    Jul 28, 2017
    Eau Claire, Wisconsin
    2007 320 Sundancer
    Twin 496. Bravo 3
    2018 3500 Chevy, Loadmaster trailer
    Raymarine Axiom, Quantum 2
    496 Mercruiser/Bravo III drives
    I needed to replace my port engine heat exchanger this year. Went with Mr. Cool. Great service and good price. Good quality product. No made in China sticker to be found! I believe there are two different sizes for the 8.1. So check your engine serial number. If just a end cap leak, that may be a easy fix. If a internal leak, ‘tubes”. I would not mess with a repair unless it was a emergency.
     
  9. Jimmy Buoy

    Jimmy Buoy Well-Known Member

    Dec 3, 2008
    Sarnia, Ontario, Canada
    340 Amberjack
    twin 8.1S 370 Hp + 4.5 Westerbeke Genset
    The end cap is easy to remove and much cheaper to replace if corroded. You'd see the coolant level dropping if it were leaking coolant (internally or externally). Mine was leaking coolant out of more than a couple of cracks in the brass tubes within the exchanger and getting flushed out the exhaust. At the time, the best replacement price was around $850 but that was 10yrs ago. Not too many aftermarket parts available at that time, but replacement solved the coolant loss issue.

    https://www.marineengine.com/parts/.../0m026000-thru-0m319190/closed-cooling-system

    See items 32,33 and 34.
     
    Last edited: Sep 13, 2019 at 11:52 AM
  10. LG111

    LG111 Active Member

    569
    Jan 4, 2015
    NW
    410
    8.1
    The caps hold back raw water.
     
  11. dmorin

    dmorin New Member

    25
    Jun 22, 2012
    Newburyport,ma
    2005 280 sundancer
    twin 4.3 mercruiser w/bravo. III drives
     
  12. dmorin

    dmorin New Member

    25
    Jun 22, 2012
    Newburyport,ma
    2005 280 sundancer
    twin 4.3 mercruiser w/bravo. III drives
    Mine was leaking at end cap too mercruiser part diagram shows bolt then metal cover rubber gasket then o ring but repair book states make sure you put o ring between metal plate and rubber gasket.mine would leak at bolt when first did per diagram going out Sunday hope it stopped.
     

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