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

  1. How.com.vn English: Step 1 Read your manual and all the safety tips.
    [1]
  2. How.com.vn English: Step 2 Read all warnings about fuel, fuel vapors and dangerous moving parts.
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  3. How.com.vn English: Step 3 Understand that you...
    Understand that you are working with explosive vapors and sparks so extreme caution must be taken to avoid explosion and or fire.
  4. How.com.vn English: Step 4 Determine your engine rotation (see tips).
    [2]
  5. How.com.vn English: Step 5 Write down your firing order for your model engine.
    This information will be listed in your factory Mercruiser Service Manual.[3]
  6. How.com.vn English: Step 6 Get familiar with your cylinder numbering system.
    GM engines do not have the same cylinder number layout as Ford engines.[4]
  7. How.com.vn English: Step 7 Label each cylinder position such as #1, #2, #3, etc.
  8. How.com.vn English: Step 8 Make sure all your spark plugs are the correct type and that they have been properly installed and tightened.
  9. How.com.vn English: Step 9 Lay out each spark plug wire in order of length.
  10. How.com.vn English: Step 10 Plan ahead so you know which plug wire will reach which cylinder.
  11. How.com.vn English: Step 11 Only install good clean spark plug wires.
  12. How.com.vn English: Step 12 Determine your distributor rotor rotation.
  13. How.com.vn English: Step 13 Label each distributor plug wire pole with White-Out if not already labeled from the factory.
  14. How.com.vn English: Step 14 Refer to your firing order to properly label the distributor cap poles.
    [5]
  15. How.com.vn English: Step 15 Double check that you have the cap properly labeled as this is where many people get confused.
  16. How.com.vn English: Step 16 Locate the #1 spark plug wire pole on your distributor cap.
    Your manual can help you ID which pole is #1.
  17. How.com.vn English: Step 17 Install the #1 plug wire to the #1 pole and neatly run the plug wire down to the #1 spark plug.
  18. How.com.vn English: Step 18 Make sure the plug wire snaps firmly onto the spark plug.
  19. How.com.vn English: Step 19 Select the correct length wire for the next cylinder number in the firing order and install it.
  20. How.com.vn English: Step 20 Install each and...
    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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  • Question
    What is the firing order for a 350 Vortec?
    How.com.vn English: Aloha27
    Aloha27
    Community Answer
    1-8-4-3-6-5-7-2
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      Tips

      • The firing order for most Mercruiser sterndrive V8 engines is 1-8-4-3-6-5-7-2
      • Go with your "gut" feeling. If it "feels" like a plug wire didn't snap onto the spark plug correctly, chances are it didn't.
      • Take the time to know which cylinder is which. For example, GM V8 engines (standard rotation sterndrive) have the #1 cylinder on the port side bank up forward and go back in the order #1, #3, #5 and #7 (all odd numbers on the port bank) and the STB bank is #2, #4, #6 and #8. Ford engines number straight back as #1, #2, #3 and #4 so don't get the order mixed up.
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      About this article

      How.com.vn 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 57,043 times.
      21 votes - 67%
      Co-authors: 10
      Updated: May 23, 2023
      Views: 57,043
      Thanks to all authors for creating a page that has been read 57,043 times.

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