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  1. #1
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    09 Pro XS 250 low idle stumble

    09 Mercury 250 Pro XS
    Serial # 1B735992
    A couple weeks ago this part failed. Mercury 8M0021043 Fuel And Water Sensor.
    Replaced it went out ran good for the day. Went out again and at low idle (5mph zone) alarm went off, long time pause in between and motor icon on smart gauge. Shut down restarted and did not sound again. Went fishing for a few hours 3 or 4 long runs no issues. Got back to the 5 mph zone and I could feel a slight surge in RPM at slight throttle, alarm went off again. Loaded up and went home. It's about a month before I can get an appointment. Anything I can look at?
    When the sensor blew out of the tank shooting fuel out of the hole, we did run it in at light throttle for a mile or so.

  2. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #2
    Need to get the engine on the Computer Diagnostic System for PRINTOUTS of the Run History and Freeze Frame (Fault) History.

    Don't rely on the "I shut off and restarted- now it's not beeping so it's good" approach, as this can easily result in expensive repairs.

    Several possibilities- one of which is a thermostat sticking open (preventing the engine from coming up to temp and potentially causing a cold-seizure).


    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).
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    #3
    Watched temp, came up to 120 in a short period. Never hits over 122.

  4. Member Especial Bryanmc57's Avatar
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    #4
    If both stats are working correctly the temp should come up to at least 130 on the initial warm up. Mine will hit 132 or so before the smartcraft temp drops.


    Honora Primum Vel Nullum Omnin Honorem

  5. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #5
    Quote Originally Posted by Bryanmc57 View Post
    If both stats are working correctly the temp should come up to at least 130 on the initial warm up. Mine will hit 132 or so before the smartcraft temp drops.
    This is NOT necessarily the case. There have been some variances in thermostat setpoints over the years, thus the "120 degree at idle minimum" temp recommendation (for an engine that uses 130 degree thermostats).

    Bassman53: Really need to confirm that BOTH banks are reaching at least 120 degrees (either by monitoring with the Computer Diagnostic System, OR by using an infrared temp gun in the center of the thermostat covers).


    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).
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    #6
    Found a recommended shop 2.5 hours away. Made the drive and dropped it off today. Hopefully know more soon.

  7. Member Especial Bryanmc57's Avatar
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    #7
    Quote Originally Posted by EuropeanAM View Post
    This is NOT necessarily the case. There have been some variances in thermostat setpoints over the years, thus the "120 degree at idle minimum" temp recommendation (for an engine that uses 130 degree thermostats).
    I stand corrected. I was just going by personal experience. My 130 degree stats have never opened under 130 when working correctly.


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  8. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #8


    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).
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    #9
    Quote Originally Posted by EuropeanAM View Post
    So shop finally called, I had them service lower unit, change all plugs, fix a leaky seal on trailer wheel.
    Then they ran it long enough for it to throw the alarm again. Comes up as #4 air injector. I guess he is not a certified Mercury mechanic so he can't dial in to mercury for assistance. So he is pulling the #4 air injector and swapping with another to see if the code changes cylinders.

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    #10
    Well he swapped air injector #4 with #2 cleared the code and can not get the code to come back up. Maybe a bad connection or do you think it might be something else?

  11. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #11
    There are two potential faults for the Air/Direct Injectors. One indicates an OPEN circuit, the other a SHORT circuit.

    Which fault (precisely) did they get?

    Connector (or corrosion in the connector) are certainly possibilities with an Open-Circuit occurring.


    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).
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    #12
    Quote Originally Posted by EuropeanAM View Post
    There are two potential faults for the Air/Direct Injectors. One indicates an OPEN circuit, the other a SHORT circuit.

    Which fault (precisely) did they get?

    Connector (or corrosion in the connector) are certainly possibilities with an Open-Circuit occurring.
    Sorry for delay in response. This home school Covid returning to school finally is killing me
    The Code was.DINJ4 open. #4 air injector open circuit.
    He tested injector with ohm meter. Removed and cleaned connections. Issue did not resolve until swapping #2 and #4 air injectors to see if fault followed the injector. After swapping the fault cleared and did not come back up. I ran a quarter tank through the boat with no issues.
    I have a hard time believing the issue resolved itself. Should I get parts in stock and ready or so you think it magically fixed itself?

  13. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #13
    You will likely end up replacing the connector for the #4 Direct Injector at some point.


    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