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  1. #1
    Join Date
    Jul 2020
    Location
    WESTPORT/GRAYLAND WASHINGTON
    Posts
    2

    Question GM 5.7L , SB350ci DISTRIBUTOR CONVERSION INFO NEEDED

    GREETINGS!,

    NEW GUY HERE. I HAVE A QUESTION REGARDING THE IGNITION SYSTEM IN MY BOAT. THE ENGINE IS A SB350ci CHEVROLET ENGINE. CURRENTLY IT HAS A MERC CRUISER THUNDERBOLT IGNITION SYSTEM IN IT. I HAVE BEEN PLAGUED WITH PROBLEMS WITH IT ALL SUMMER AND IT'S GETTING EXPENSIVE BUYING REPLACEMENT PARTS FOR THE THUNDERBOLT IGNITION SYSTEM . I'M WONDERING IF I CAN JUST CHANGE THE DISTRIBUTOR IN IT FROM THE THUNDERBOLT SYSTEM TO A STANDARD GM HEI
    (BIG CAP HEI W/ COIL IN THE CAP)DISTRIBUTOR THAT HAS A VACUUM ADVANCE RATHER THAN AN ELECTRONICALLY CONTROLLED ADVANCE SYSTEM? IS THIS POSSIBLE? IS THERE A CONVERSION PROCEDURE OR A KIT FOR DOING THIS OR IS IT NOT A GOOD IDEA? I APPRECIATE ANY AND ALL ADVICE & INFO ANYONE CAN GIVE ME.

  2. #2
    Join Date
    Mar 2009
    Location
    Portland, Oregon,
    Posts
    12,087

    Default Re: GM 5.7L , SB350ci DISTRIBUTOR CONVERSION INFO NEEDED

    Do not use an automotive vacuum advance distributor!

    If you prefer to get away from EST, look at the Mallory YLM624AV, or one of the many other options.



    .
    Last edited by RicardoMarine; 07-03-2020 at 11:50 PM.
    Rick ... aka Ricardo..... AQ series Volvo Penta repair
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP drives

    "Intellectual growth should commence at birth and cease only at death." Albert Einstein

    Please... no PMs! Post your questions on the forum.

  3. #3
    Join Date
    Jul 2020
    Location
    WESTPORT/GRAYLAND WASHINGTON
    Posts
    2

    Default Re: GM 5.7L , SB350ci DISTRIBUTOR CONVERSION INFO NEEDED

    Quote Originally Posted by RicardoMarine View Post
    Do not use an automotive vacuum advance distributor!

    If you prefer to get away from EST, look at the Mallory YLM624AV, or one of the many other options.



    .
    Ok. Just for the sake of knowledge, may I ask why?
    IT TAKES A BIG MAN TO CRY. BUT IT TAKES A BIGGER MAN TO LAUGH AT THAT MAN!

  4. #4
    Join Date
    Mar 2009
    Location
    Portland, Oregon,
    Posts
    12,087

    Default Re: GM 5.7L , SB350ci DISTRIBUTOR CONVERSION INFO NEEDED

    Quote Originally Posted by POLECAT13 View Post
    Ok. Just for the sake of knowledge, may I ask why?
    Yes you may.

    1...... the automotive ignition distributor is not "ignition source protected". In other words, there is nothing to prevent an escaping internal spark from igniting gasoline vapors.

    2...... the advance curve is incorrect for Marine Engine use and may cause engine damage. I.E., ignition induced Detonation, especially with the GM Full Dished piston build.

    3...... t
    he marine engine is always under load, so there is no minimum throttle position that makes for manifold pressure that could take advantage of vacuum advance.
    It is a fuel economy device for the automotive engine.



    .
    Last edited by RicardoMarine; 07-04-2020 at 07:38 AM.
    Rick ... aka Ricardo..... AQ series Volvo Penta repair
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP drives

    "Intellectual growth should commence at birth and cease only at death." Albert Einstein

    Please... no PMs! Post your questions on the forum.

  5. #5
    Join Date
    Dec 2006
    Location
    Greenfield Me. USA
    Posts
    6,073

    Default Re: GM 5.7L , SB350ci DISTRIBUTOR CONVERSION INFO NEEDED

    Ayuh,..... The Delco Voyager is a reasonably priced, fine ignition swap too,....
    Any Grease is Better,... Than No grease at All....

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