Announcement

Collapse
No announcement yet.

98 GTX 951, Ign Timing Retards w/Eng Hot

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • 98 GTX 951, Ign Timing Retards w/Eng Hot

    98 GTX Ltd 951

    The engine runs great when first started, but after a few minutes of running intermittently loses power (can't even get on plane).

    The problem:
    1. Ignition timing is normal (3.60mm BTDC) when cold, but backs up all the way to 0mm BTDC, when it starts running bad.
    2. Curiously, the timing problem seems somehow related to throttle movement:
    - It first appears after throttle is closed after a high speed run.
    - Working the throttle carefully back/forth across mid-throttle seems to sometimes restore proper timing, whereas simply going to WOT guarantees the timing will retard.
    3. All of these observations where made with a timing light, with the boat running--in water--while tethered to the dock.

    Questions:
    1. Are there any known issues with this engine regarding intermittent timing retard?
    2. What effect does the engine temp sensor have on ignition timing? Again this problem doesn't occur with a cold engine.
    3. The service manual mentions a "hall-effect throttle sensor" installed in the throttle cable and further states that this effects ignition timing. However, I could not find any such sensor on the boat.
    4. I hate to go out and buy the expensive ignition control module (which also controls everything else on the boat) if there is a simple explanation.

    Thanks,

    Steve
    Last edited by vznx1w; 08-04-2004, 10:19 AM. Reason: typo

  • #2
    Re: 98 GTX 951, Ign Timing Retards w/Eng Hot

    Look under the oil tank to see if you have the throttle position switch (TPS) type throttle cable. It sends a message via some electrical wires coming from it to the computer (MPEM) that retards the ignition at high rpm. If you have a TPS ( not all models do), then it needs to be either adjusted or replaced.

    If you don't have TPS, then the problem is probably the MPEM is malfunctioning.
    Bill O'Neal <br>
    WCM
    <a href="http://www.watercraftmagic.com"

    Comment


    • #3
      Re: 98 GTX 951, Ign Timing Retards w/Eng Hot

      Thanks Bill,

      I'll check again for the TPS sensor.

      If I do need to replace MPEM, can I simply get an aftermarket (less expensive!?) ignition module instead? Will these units run the ignition independant of the MPEM--do they connect directly to the Mag and Ign coil?

      Can you recommend a brand.

      Thanks again for your quick reply.

      Steve

      Comment


      • #4
        Re: 98 GTX 951, Ign Timing Retards w/Eng Hot

        No, the aftermarket ignitions work in conjunction with a good MPEM.
        The exception would be total loss, but then you lose everything else controlled by the mpem, like the guages, rave solenoid, VTS, ect.
        Bill O'Neal <br>
        WCM
        <a href="http://www.watercraftmagic.com"

        Comment

        Working...
        X