How to Replace Your Mercruiser Spark Plug Wires

Replacing your spark plug wires can be easy if you take your time and know your engine information.

Steps

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    Read your manual and all the safety tips.[1]
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    Read all warnings about fuel, fuel vapors and dangerous moving parts.
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    Understand that you are working with explosive vapors and sparks so extreme caution must be taken to avoid explosion and or fire.
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    Determine your engine rotation (see tips).[2]
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    Write down your firing order for your model engine. This information will be listed in your factory Mercruiser Service Manual.[3]
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    Get familiar with your cylinder numbering system. GM engines do not have the same cylinder number layout as Ford engines.[4]
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    Label each cylinder position such as #1, #2, #3, etc.
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    Make sure all your spark plugs are the correct type and that they have been properly installed and tightened.
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    Lay out each spark plug wire in order of length.
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    Plan ahead so you know which plug wire will reach which cylinder.
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    Only install good clean spark plug wires.
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    Determine your distributor rotor rotation.
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    Label each distributor plug wire pole with White-Out if not already labeled from the factory.
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    Refer to your firing order to properly label the distributor cap poles.[5]
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    Double check that you have the cap properly labeled as this is where many people get confused.
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    Locate the #1 spark plug wire pole on your distributor cap. Your manual can help you ID which pole is #1.
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    Install the #1 plug wire to the #1 pole and neatly run the plug wire down to the #1 spark plug.
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    Make sure the plug wire snaps firmly onto the spark plug.
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    Select the correct length wire for the next cylinder number in the firing order and install it.
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    Install each and every plug wire one at a time double checking it's position in the firing order on the cap and on the spark plug.
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Community Q&A

  • Question
    What is the firing order for a 350 Vortec?
    Aloha27
    Aloha27
    Community Answer
    1-8-4-3-6-5-7-2
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Warnings

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References

  1. ↑ https://www.mercurymarine.com/en/asia/service-and-support/owners-resources/
  2. ↑ https://www.melling.com/wp-content/uploads/2017/03/marine-engines-standard.pdf
  3. ↑ https://www.perfprotech.com/blog/tech-articles/find-all-your-mercuiser-secifications-here-such-as-engine-fluid-capacities-horsepower-ratings-and-wiring-diagrams-5886
  4. ↑ https://www.perfprotech.com/blog/boat-and-engine-technical-tips/marine-engines/mercruiser-engines-block-id-codes-4-cylinder-marine-engines
  5. ↑ http://chicagoengines.com/marine/marine-firing-orders.aspx

About This Article

wikiHow is a “wiki,” similar to Wikipedia, which means that many of our articles are co-written by multiple authors. To create this article, 10 people, some anonymous, worked to edit and improve it over time. This article has been viewed 56,204 times.
20 votes - 65%
Co-authors: 10
Updated: October 21, 2021
Views: 56,204
Categories: Boats
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