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  1. #1

    Default Corrosion on Mercruiser 350 Magnum

    Hello,

    I apologize if this is a stupid question. I'm not a mechanic and have spent very little time around engines and boats. I admit I'm an idiot, so please save any eye-rolling.

    I have a 1994 20' Bluewater with a Mercruiser 350 Magnum Alpha One engine and just noticed some corrosion on the engine between casing. Does anyone know what this might be from? And what should be done about it? It appears on the compartments on both sides of the engine (though am not sure what compartments these are).

    See attached pics.

    Any insight would be great. Thank you!

    Click image for larger version. 

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  2. #2
    Join Date
    Sep 2010
    Location
    Jersey Shore
    Posts
    4,635

    Default Re: Corrosion on Mercruiser 350 Magnum

    It is the exhaust and it is time to replace it. As we say..."if it is leaking on the outside it is leaking on the inside"......
    Chris
    Dockside Marine Services
    Jersey Shore.
    Mercruiser/Mercury Certified
    Let the insanity begin.

  3. #3

    Default Re: Corrosion on Mercruiser 350 Magnum

    Gotcha...thank you for the quick reply!

  4. #4
    Join Date
    Jun 2006
    Location
    Spotswood, NJ, USA
    Posts
    3,861

    Default Re: Corrosion on Mercruiser 350 Magnum

    only if there cast iron, some were SS and it could be the manifold surface going bad. Drain the manifold and riser, remove the riser and inspect everything

  5. #5
    Join Date
    Sep 2010
    Location
    Jersey Shore
    Posts
    4,635

    Default Re: Corrosion on Mercruiser 350 Magnum

    And we do not reinstall Stainless Steel elbows with cast iron manifolds for this reason.....They rot and leak. Replace all SS with cast Iron.
    Chris
    Dockside Marine Services
    Jersey Shore.
    Mercruiser/Mercury Certified
    Let the insanity begin.

  6. #6

    Default Re: Corrosion on Mercruiser 350 Magnum

    Thank you both. You've both been very helpful and have given me the info I need to work this out.

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