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  1. #1

    Default Distributor Advance issue

    I am experiencing an ignition problem that I'm hoping someone can shed some light on. I have a boat with twin big block Chevy 454 V8 engines.

    * One of the engines has 8 degrees BTC of initial advance (at idle) and 34 degrees BTC of total advance at 2800 rpm. This is great, the engine performs perfect.

    * The other engine has 8 degrees BTC of initial advance (at idle) and 16 degrees BTC of total advance at 2800 rpm. This engine is not performing to its potential. While at full load/full throttle, it is 700 rpm down from the other engine.

    Here is where my confusion begins. These distributors have no mechanical or vacuum advance mechanism, nor do they have any outside control box or computer. As seen in the pictures, there are only two connection ports, as 2 pin, and a 4 pin, only one of which is used (the 2 pin port). So my question is how do these distributors introduce more timing advance as the rpm goes up? Are the ignition modules in the distributor pre-programmed to increase the timing as rpm increases? I have included all the numbers I can find from the distributor that seems to be falling short of total advance.
    - Electronic / Mallory YLE 624 AV
    - Listed 339F
    - SAE J1171
    - Module # TRANSPO-CN
    - DM15 5HD-3029

  2. #2
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    6,761

    Default Re: Distributor Advance issue

    34 degrees is a bit much....32 degrees is as high as I go....on a stock engine.

    16 degrees total is your problem - good job there!!

    I'm pretty sure you have a mechanical advance inside the distributor - vacuum advances aren't used on inboards...

    When you remove the distributor cap, can you rotate the rotor about 10-12 degrees?

  3. #3

    Default Re: Distributor Advance issue

    Quote Originally Posted by makomark View Post
    34 degrees is a bit much....32 degrees is as high as I go....on a stock engine.

    16 degrees total is your problem - good job there!!

    I'm pretty sure you have a mechanical advance inside the distributor - vacuum advances aren't used on inboards...

    When you remove the distributor cap, can you rotate the rotor about 10-12 degrees?

    Nope on the rotating the rotor. There is not mechanical adjustments above the plate (well). Neither above or below. Onloy a two pin & four pin connection of which is only using the two pin on both engine setups.

  4. #4
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    6,761

    Default Re: Distributor Advance issue

    ok...you made me look it up....

    supposed to be a drop in replacement for the DELCO EST distributor....same hookup.

    So that means the rotor is locked to the gear and all the advance function is in the module.....quickest diagnostic approach would be to swap modules between distributors and see if the 'limited advance' follows the module.

    I'm surprised the 'good' module provides that much advance....many won't get near that when operated standalone.

  5. #5

    Default Re: Distributor Advance issue

    Makomark,

    Thanks for the prompt responses and I replaced the distributor with a new electronic MSD and a significant improvement. I think that the starboard engine had not performed to it potential for some period. This came to light when I would back into or slip and the engine would stall periodically, thus checked the timing ad digital Tach and a friend diagnosed the advance issue. In short, 5 knots faster at 3400 and with both set at 34* advance. I would like find the correct part for the existing distributor so the mains match, however to date it's like finding Sasquatch.
    Thanks again.

  6. #6
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    6,761

    Default Re: Distributor Advance issue

    http://www.marineengine.com/newparts...m=SIE18-5107-1

    The link above is to the Delco EST module - which is what your YLE is supposed to be a clone of. The picture is of a Transpo (aftermarket) module.....many have found the original DELCO modules to be 'well behaved' - specifically, more repeatable. if your 'bad' module looks like the one in the link, you can find it searching for Delco EST.


    In the interim, glad you are running again (& probably burning less fuel too)....

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