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Thread: Seized plugs

  1. #1

    Join Date
    Sep 2006
    down under

    Seized plugs

    I have noticed that more than a few people have come across seized sparkies. This is easily preventable so I thought I would post up a quick guide.

    If your plugs have never seen antisieze, (wich seems to be 99% of boats sold in the USA) this is what you need to do.

    Buy some nickel based antisieze. I don't reccommend the more common copper based stuff because of galvanic corrosion. (google it, this is not a science lesson) Rule of thumb is antisieze compound is colour coded. if the stuff is silver/grey, all is cool. If it's goldish, best to be avoided.

    Remove plugs. (if they don't come out, don't force them and stay tuned for future thread)

    Smear a thin coating of antisieze on threads and install plugs to finger tightness.

    Remove plugs, install another thin smear on threads and re-install and tighten. Don't overtighten! Used plugs, use about as much torque as you would use to close an old style faucet tap. New plugs, approx 1/8 turn from seated. (I know that the NGK box says 1/4 turn but thats too much on a M10 plug thread)

    Why do it twice?, I hear you ask.

    The first installation puts a coating of antisieze on the female (head) threads that dosen't properly coat the lower few threads near the combustion chamber. By backing it out and re-applying, the second installation ensures that the antisieze compound migrates all the way to the bottom.

    I do this procedure at pre delivery and as far as I know, every competent dealer of all brands does the same in Australia due to the fact that almost all Aussie ski's are saltwater boats.

    Happy riding!

  2. #2
    Aluminum contains a portion of copper in the alloy. I've used copper anti-seize for 30 years with spark plugs and had no problems. Graphite stuff works fine too. As a competent method I use a torque wrench with factor spec by compensation for the lubricant as a reduction to the spec. (normal workman practice)

    Copper stuff is recommended for sparkplugs installed in aluminum heads. It's even got a MIL spec!

    And here is the nickel shit not recommended for spark plugs.

    This copper stuff is recommended for marine use.

    Then there is the graphite stuff. Then again some could screw up.

    Pick your poison but I think I'd trust the product information and don't over do it with the products or tightening.
    Here's what Autolite says about using anti-seize (snicked off the net somewhere):

    We do not recommend the use of any anti seize products for installing spark plugs. Anti seize compounds are typically composed of metallic,
    electrically conductive ingredients. If anti seize compounds come in
    contact with the core nose of the plugs, it can lead to a misfire condition.
    Anti seize compounds can also have a torque multiplying effect when
    installing plugs. This can lead to thread distortion and thread galling
    resulting in cylinder head damage. Autolite spark plugs are nickel plated
    to resist the effects of corrosion and seizing. However, plug seizure is
    aggravated further when steel plugs are installed into aluminum cylinder
    heads for a long period of time.

    Here's what AC/Delco says:

    Do not use any type of anti-seize compound on spark plug threads. Doing this will decrease the amount of friction between the threads. The result of the lowered friction is that when the spark plug is torqued to the proper specification, the spark plug is turned too far into the cylinder head. This increases the likelihood of pulling or stripping the threads in the cylinder head. Over-tightening of a spark plug can cause stretching of the spark plug shell and could allow blowby to pass through the gasket seal between the shell and insulator. Over-tightening also results in extremely difficult removal.

  3. #3
    the wotman likes boobs wotman's Avatar
    Join Date
    Mar 2009
    Could this thread be stickyed???????

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