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  1. #1
    Join Date
    Feb 2006
    Location
    Huntington Beach, California, USA
    Posts
    5

    Default Mercruiser 454 MIE block off gaskets

    I have coolant leaking past the block off gasket, is it advisable to remove, clean up and install new gaskets ?
    Block off gasket at elbow to manifold connection, which one to use ?
    Green one's, as I understand it use no sealants ? Aviation gasket sealer / Permatex - 2. New parts only?
    Graphite one's by Quiksilver, don't know much about them.
    Stainless steel block off plate between two gaskets, is this an outdated method ?

    Thank you

  2. #2
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    6,767

    Default Re: Mercruiser 454 MIE block off gaskets

    Probably would get more opinions had this been posted in the mercruiser section......

    So, from your description, this is an older style, fresh water cooled install and the leak is at the exhaust manifold-exhaust elbow joint?

    I prefer the older approach, gaskets and a stainless blockoff plate....yes, you have to disassemble the connection and its usually less mess if you drain some coolant out of the manifold. the cast iron mating surfaces have to be true and solid to get a good seal (sometimes draw filing is in order). many times, the elbow side is eroded...and they should be changed ~ 5 years, especially if used in the salt....

    I prefer the aviation sealer when assembling the "sandwich"....a minor leak on the raw water side really won't hurt anything except the cosmetics....and be consistent when you torque the fasteners.....drawn them up evenly and you should be good to go...

  3. #3
    Join Date
    Dec 2006
    Location
    Chaumont Bay, N.y., USA
    Posts
    5,148

    Default Re: Mercruiser 454 MIE block off gaskets

    Quote Originally Posted by makomark View Post
    Probably would get more opinions had this been posted in the mercruiser section......

    So, from your description, this is an older style, fresh water cooled install and the leak is at the exhaust manifold-exhaust elbow joint?

    I prefer the older approach, gaskets and a stainless blockoff plate....yes, you have to disassemble the connection and its usually less mess if you drain some coolant out of the manifold. the cast iron mating surfaces have to be true and solid to get a good seal (sometimes draw filing is in order). many times, the elbow side is eroded...and they should be changed ~ 5 years, especially if used in the salt....

    I prefer the aviation sealer when assembling the "sandwich"....a minor leak on the raw water side really won't hurt anything except the cosmetics....and be consistent when you torque the fasteners.....drawn them up evenly and you should be good to go...
    Ayuh,.... I ain't looked, but is there a freshwater set up done with the newest greatest idea from Mercruiser, the Dry joint system,..??

    Seems like it oughta adapt reasonably easy, 'n without much fuss,....

    In the pictures on-line, I can't tell if the manifolds are tapped for plugs in the water ports,...
    Also wonderin' if the bolt pattern matches the ole wet-joint risers/ elbows,..??
    Last edited by bondo; 03-30-2015 at 06:38 PM.
    Any Grease is Better,... Than No grease at All....

  4. #4
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    6,767

    Default Re: Mercruiser 454 MIE block off gaskets

    As far as I know, they never made a 7.4 with a dry joint setup....I'd suspect you could retrofit something newer onto the older engines but it won't be economical...probably better off searching the www to find a set of stainless elbows - I love mine..

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