2002 340 DA 6.2 MX MPI iginition issue

Discussion in 'General Maintenance/Repair Questions' started by GuyFM, Mar 29, 2020.

  1. GuyFM

    GuyFM New Member

    8
    Jul 18, 2019
    2002 340 Sundancer
    Mercruiser 6.2MX
    2002 Sea Ray 340 Sundancer with twin Mercruiser 6.2 MX MPI motors with 500 hours, having this issue above 3,000 rpm. Marina service has set timing, replaced cap & rotor, spark plugs and wires and they can not figure out this issue. Batteries are new, new alternator, fresh fuel (in fact they replaced both inline filters and water/separator filters) and this issue persists.

     
  2. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor GOLD Sponsor

    Apr 21, 2009
    PA
    Various
    Various
    It's changing RPM so fast... are the engine RPM's ACTUALLY changing?

    If not, this isn't an engine issue which is why changing the things they did made no difference. Try "exercising" the cylinder selector switch on the back of the tach. Make sure you end back up on "8".
     
    Craig, Chris-380 and techmitch like this.
  3. Espos4

    Espos4 Well-Known Member

    Jan 1, 2017
    Long Island NY
    2007 240 Sundeck
    350 MAG Bravo 3 W/DTS
    How does it sound and perform? Don’t look at the gauge, listen and feel, does it hit your rated WOT rpm?

    I agree with Lazy Daze. Could just be a gauge issue.
     
  4. GuyFM

    GuyFM New Member

    8
    Jul 18, 2019
    2002 340 Sundancer
    Mercruiser 6.2MX
    Thank you for your questions. It looks like a bad tachonometer but it is not an instrument issue, the tach is reading correctly. There is a loss of power as shown, it's as if the ECU is, for lack of a better term, "bumping" into limp mode. I'm not sure what the correct term is. My GM dealer friend suggests that the 6.2 MPI is "extremely sensitive" when it comes to setting the timing on these 6.2 MPIs. I thought I'd post here for ya'll thoughts. Could the marina simply not know how to set base timing? Or should I start swapping parts between the perfectly running starboard running engine?
     
  5. Spark600

    Spark600 Active Member

    148
    Dec 28, 2013
    Long Island NY
    2008 Sundancer with 496 SeaCore Bravo 3
    Kohler Generator
    Mercury dinghy
    496 SeaCore Bravo 3
    Maybe a bad ground wire.
     
  6. Wanderer 290

    Wanderer 290 Active Member

    203
    Jul 1, 2019
    01 sea ray 290 sundancer
    Twin 5.7 b3’s
    May be the ignition sensor? The original sensor is a common fail item due to poor grounding.
     
  7. GuyFM

    GuyFM New Member

    8
    Jul 18, 2019
    2002 340 Sundancer
    Mercruiser 6.2MX
    Are you talking about the sensor that is inside the distributor under the rotor? If so, this model year engine does not use that sensor. If not, can you please elaborate? Thank you!
     
  8. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    Post up an engine # so we can see what ignition system you have
     
  9. Wanderer 290

    Wanderer 290 Active Member

    203
    Jul 1, 2019
    01 sea ray 290 sundancer
    Twin 5.7 b3’s
    Yes, sensor under the cap is what I was speaking of...
     
  10. GuyFM

    GuyFM New Member

    8
    Jul 18, 2019
    2002 340 Sundancer
    Mercruiser 6.2MX
    Serial number OM313031 350 MAG MX 6.2L MPI INBOARD (2002) that ignition sensor is not used. Again, thank you for your input!

    Here is another video of the issue
     
    Last edited: Mar 31, 2020
  11. speakrdude

    speakrdude Well-Known Member

    Feb 21, 2009
    Northwest Arkansas
    2002 Sea Ray 340 DA
    Raymarine C80 Tri Data
    twin 6.2 MX MPI
    My port engine (2002-340-6.2’s-v-drives) started doing the same thing with anything over 3000rpms yesterday, after filling up fuel tank. All fresh filters last Sumer. Was thinking maybe a water/dirt disturbance after fueling.
    Keep us posted.
     
  12. GuyFM

    GuyFM New Member

    8
    Jul 18, 2019
    2002 340 Sundancer
    Mercruiser 6.2MX
    We are still working on this issue and will let you know. Make sure your distributor has not come lose - these motors are sensitive to timing. I recently discovered that Mercury had a service they offered around 2006 to reprogram the ECU to "loosen" the parameters for limp mode due to timing control being too tight, for lack of a better term.
     
  13. GuyFM

    GuyFM New Member

    8
    Jul 18, 2019
    2002 340 Sundancer
    Mercruiser 6.2MX
    There is an intermittent arc under load (>3000rpm) on the coil. The plugs, wires, cap and rotor are new so re-checking plug gaps and will take a very close look at the coil checking for a carbon track/crack and will do Ohm test of the new Merc wires. The marina service said they swapped coils and the problem did not follow the coil. Will update again.
     

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