Results 1 to 6 of 6
  1. #1
    Member
    Join Date
    Nov 2009
    Location
    Keystone Lake, OK
    Posts
    212

    Mercury 250 pro Xs surging after fuel rail replacement

    ‘09 Pro XS serial number 1b751133
    After replacing my compressor I had to replace fuel rails and 3 air injectors. I finally got it on the water today. Seemed to idle fine (as it did on the hose). After warm up it wanted to die when I put it in gear. I tried to take off and it would start surging/bucking at around 3000 rpm. It would do it a few times then get up
    on plane and act normal. It did what is shown. In the video every time I tried to plane out. I did replace spark plugs before this and gapped to .042-.044. Thoughts on if it’s spark or fuel?

    https://youtu.be/jJUVwHRgv9A

  2. Member
    Join Date
    Sep 2019
    Location
    Mathews, VA
    Posts
    15
    #2
    Id start with Checking your fuel and air pressure.

  3. Member
    Join Date
    Feb 2009
    Location
    Worcester, MA
    Posts
    791
    #3
    Sounds starved for fuel to me. That is kind of what it sounded like when I had a bad fuel filter. Make sure there's no fuel in the air line and no air in the fuel line by pressing the shrader valve after running for 10 seconds. Air is on the port side, fuel on the starboard side. also check to make sure all your connectors to all 12 injectors are on good since you took the whole fuel rail off.

    are you getting close to max RPM when it gets on plane?
    Chad Snow / Massachusetts
    2007 Ranger Reata 210 - Mercury Optimax 225 (#1B446134) - 12' Talons
    Carbon12’s @ Bow w/ AT- live 12 w/ 3D & live 7 @ Helm


  4. Member
    Join Date
    Nov 2009
    Location
    Keystone Lake, OK
    Posts
    212
    #4
    Ok so after calling around and not being able to get it in anytime soon I threw some parts at it. I wasn’t able to get air and fuel pressures tho. But I rebuilt the pulse fuel pump, checked spark plugs, and replaced the fuel filter. The boat sat for nearly six months after a compressor replacement waiting for fuel rails and injectors to be tested. I ended up with new rails and three new (air) injectors but I’m still dealing with the same surge/ bog since replacement. It happens at about 3500 rpms when getting out of the hole. It’s inconsistent in its severity. After replacing the fuel filter today I ran it with mixed results but upon returning to the ramp I seem to have developed an idle flare when putting it in neutral. It is corrected after shutting the motor down and restarting. I can’t get the boat in anywhere soon and I’m at a loss. Going to check fuel lines tomorrow but they were upgraded a few years ago.

    I drained all of the fuel from the tanks when I knew it was to sit for an extended period. These are problems I never experienced before the boat sat this long. Any more advice is appreciated.

  5. Member lpugh's Avatar
    Join Date
    May 2009
    Location
    Sacramento Ca
    Posts
    5,164
    #5
    Test the fuel for water and alcohol content. Perform a tps sweep test as well as the pressure tests
    Test available voltage from coils also
    Thank You Leon Pugh

  6. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
    Join Date
    Apr 2008
    Location
    Greenville, SC (US)
    Posts
    94,941
    #6
    Ray- that "sounds" electrical. I've be looking at several items, specifically:

    1. Make sure the small black sleeve is present on the RETURN fuel line, where it goes into the back of the VST. If it is missing, fuel can become AERATED.

    2. Check EVERY injector connector/plug for it's rubber SEAL. A missing seal will cause vibration and a potential of an intermittent connection.

    3. Verify coils and plug wires are firmly connected, and that no plug wires are rubbing or arcing against any objects.

    4. Inspect spark plugs and perform a spark test.

    5. Obtain very accurate Air/Fuel Pressure Tests (as well as LEAKDOWN at 5/10/15 seconds after engine shutdown).

    6. Make sure throttle cable is consistently returning the throttle arm firmly against it's idle stop.

    My "gut" is leaning towards something in #1 - 4.


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
    Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor