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  1. #1
    Join Date
    Aug 2019
    Location
    Arden, DE
    Posts
    25

    Default 97 Merc 90elpto Weak Spark all plugs

    On my spark plug tester, I get an orange spark with al spot of white in the center. I think I've read that it should be white (even blue white.) It is stronger than it was. How should the sparks it look?
    I've replaced:
    trigger (with CDI 134-4512-3)
    3 CDMs (with CDI 114-7509)
    stator (with CDI 174-2075K2) (old one was CDI 174-832075K1) It's measuring 462ohms. Is this right?
    Flywheel replaced last summer.
    I have a voltage regulator (CDI 194-5279), but I don't think that affects the spark; does it?
    Also, my kill wire is shutting down the engine, disconnected from the harness.
    Voices of experience please?
    THanks,
    Denis

  2. #2
    Join Date
    Nov 2011
    Location
    tennessee
    Posts
    4,519

    Default Re: 97 Merc 90elpto Weak Spark all plugs

    Why did you replace all this? What problems are you having?
    Pappys Sales and Service
    Owner and Factory Certified Technician
    Former racer KDBA (Kentucky Drag Boat Association)

  3. #3
    Join Date
    Nov 2011
    Location
    tennessee
    Posts
    4,519

    Default Re: 97 Merc 90elpto Weak Spark all plugs

    Why did you replace all this? Have you tested DVA output as ohms test is not trusted in my book. Seen to many parts pass OHM spec and still be bad...
    Pappys Sales and Service
    Owner and Factory Certified Technician
    Former racer KDBA (Kentucky Drag Boat Association)

  4. #4
    Join Date
    Aug 2019
    Location
    Arden, DE
    Posts
    25

    Default Re: 97 Merc 90elpto Weak Spark all plugs

    Quote Originally Posted by faztbullet View Post
    Why did you replace all this? Have you tested DVA output as ohms test is not trusted in my book. Seen to many parts pass OHM spec and still be bad...
    Good question Faztbullet.
    I replaced the trigger because of blk and wht wires looked melted at or near touching block. Did the stator at same time because of low ohms and 20 year age. I know so little about the history of this engine, but it's at least 23 years old, multiple owners, and alot of evidence it's not been loved. Flywheel had broken magnets. It starts right up, but only with the BLK/YEL unplugged near the CDMs. (The in-line bullet plug) The in-line plug tester is a Lisle and shows orange on all 3 plugs. I do get a blue-white spark across outside insulation to metal though.
    I have the wiring harness unplugged, at the engine, so that the remote control is out of consideration. With engine running, I reconnect the BLK/YEL bullet plug, and the engine kills. So, I must have a short in the harness plug; right? Assumed short to something else; no joy.
    But, I just disconnected the PPL bullet connector in-line from the disconnected harness to what I believe is the Oil Warning Module. NOW the BLK/YEL line does NOT kill the engine. Do I assume that the Oil Module is providing some sort of ground through the disconnected harness?
    Thanks for your help.
    Denis

  5. #5
    Join Date
    Nov 2011
    Location
    tennessee
    Posts
    4,519

    Default Re: 97 Merc 90elpto Weak Spark all plugs

    A oil module does not hook into ignition but a rev limiter does!!!!
    Pappys Sales and Service
    Owner and Factory Certified Technician
    Former racer KDBA (Kentucky Drag Boat Association)

  6. #6
    Join Date
    Aug 2019
    Location
    Arden, DE
    Posts
    25

    Default Re: 97 Merc 90elpto Weak Spark all plugs

    Quote Originally Posted by faztbullet View Post
    A oil module does not hook into ignition but a rev limiter does!!!!
    Is a rev limiter part of a standard 90 elpto? Or, is it a modification?

  7. #7
    Join Date
    Aug 2019
    Location
    Arden, DE
    Posts
    25

    Default Re: 97 Merc 90elpto Weak Spark all plugs

    I can't find a rev limiter anywhere. THough the parts list for my year, model and serial # does show one, I can't find a spot for it on the block.

  8. #8
    Join Date
    Aug 2019
    Location
    Arden, DE
    Posts
    25

    Default Re: 97 Merc 90elpto Weak Spark all plugs

    Quote Originally Posted by pyrodenis View Post
    I can't find a rev limiter anywhere. THough the parts list for my year, model and serial # does show one, I can't find a spot for it on the block.
    Ah!. looks like it's buried behind the tilt relays.

  9. #9
    Join Date
    Aug 2019
    Location
    Arden, DE
    Posts
    25

    Default Re: 97 Merc 90elpto Weak Spark all plugs

    Quote Originally Posted by pyrodenis View Post
    Ah!. looks like it's buried behind the tilt relays.
    To continue my lonely madness; that was the oil warning module. Still haven't found the rev limiter. Should be easy, since it'll have a BLK/YLW to join with those to CDMs.

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