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Results 1 to 5 of 5
  1. #1

    Question Mercury Optimax 225 DFI : IDLE PROBLEM

    I encounter a problem on my Mercury 225 hp.
    Idle is unstable.
    the engine starts badly at 4000 rpm, it goes down to 3500 rpm then goes back to 4000 rpm .......
    Fuel pressure : 90psi
    Air Pressure : 80psi

    I don.t understand.!!!!
    Can you help me ?

    Sorry for the translation
    I.m French.

  2. #2
    Join Date
    Aug 2006
    Location
    SW Ohio, USA
    Posts
    10,329

    Default Re: Mercury Optimax 225 DFI : IDLE PROBLEM

    Check the wire connectors at each temperature sensor for corrosion. A wandering engine idle can be caused by a loss of temperature readings which confuses the engine computer because it does not know the temperature of the air or engine block.

    PS: Your english is easily understood.
    Fix minor things (replace wear items for preventative maintenance.) that cause major problems before they break.

  3. #3

    Default Re: Mercury Optimax 225 DFI : IDLE PROBLEM

    Thank you so much !
    I will immediately check all engine temperature sensors.
    How many sensors on the engine? Four?
    What is the role of each?

  4. #4
    Join Date
    Aug 2006
    Location
    SW Ohio, USA
    Posts
    10,329

    Default Re: Mercury Optimax 225 DFI : IDLE PROBLEM

    My Merc. manual is for 150 HP and under but I assume the electronics are similar. Use the engine serial number to search above in Merc. outboard parts schematics to see how many and where the sensors are located.
    Fix minor things (replace wear items for preventative maintenance.) that cause major problems before they break.

  5. #5
    Join Date
    Sep 2010
    Location
    Jersey Shore
    Posts
    3,227

    Default Re: Mercury Optimax 225 DFI : IDLE PROBLEM

    It's the tracker valve diaphragm. Almost guaranteed. When this part wears out (gets a hole in it), it leaks fuel into the air rail.
    Last edited by Docksidemarineservices; 02-21-2013 at 10:44 AM.
    Chris
    Dockside Marine Services
    Jersey Shore.
    Let the insanity begin.

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