Mercury pro xs 115hp

  • Todd Benjamin Milde
    Posts: 2
    December 31, 2018 at 4:06 pm #1822026

    Hi guys, just brought a almost new boat with 115 mercury pro xs, 85hrs and after having multiple minor issues fixed i took the wife and dogs out to watch the firewrx last night from the water and on the way in the motor started missing and running realy crap like a old 2 banger, im nearly ready to drive it back into dealership and lose my narner this is no 8 issue in 3 months what could it be any help would be great as i dont want to see them again if i can help it.

    brad-o
    Mankato
    Posts: 410
    December 31, 2018 at 4:10 pm #1822031

    I have the same motor with about 25 hours no issues. I would check spark plugs, Spark wires, and coil packs first.

    Tom P.
    Whitehall Wi.
    Posts: 3526
    December 31, 2018 at 5:54 pm #1822058

    Not sure on your newer Opti but mine when I first turn the key on I have to wait a few seconds as there is a self test that runs. If I do not wait it will run like crap until I shut it off and wait for the self test restart it runs perfect. One issue I have had with mine is bad spark plugs even brand new ones bad right out of the box. Is it still under warranty if so I woul find a good Merc mechanic and get it in. One very important thing with the Optis it being a tight clearance engine DO NOT put the throttle down hard until the engine is warm.

    Todd Benjamin Milde
    Posts: 2
    January 4, 2019 at 4:55 pm #1823159

    They reckon it was a foweld up bottom sparkplug but it doesnt make sense from a fuel injected motor under 100 hrs with perfect comp.

    Iowaboy1
    Posts: 3791
    January 4, 2019 at 5:20 pm #1823160

    its not that unusual to fowl a plug in that motor,cheap oil,ethanol gas,prolonged idling,etc.will do it in short order.
    remember also that the bottom cylinder receives cooling water before the rest of the cylinders so it tends to run a bit cooler as a result and most often will be the first cylinder to foul a plug.

    put good non oxy gas in it,make sure you are running the right oil,take it out,warm it up good and put it through its paces.

    Tom P.
    Whitehall Wi.
    Posts: 3526
    January 5, 2019 at 10:01 am #1823274
    Todd Benjamin Milde wrote:

    They reckon it was a foweld up bottom sparkplug but it doesnt make sense from a fuel injected motor under 100 hrs with perfect comp.

    Reason it could be fowled is a bad plug as I stated above I have had brand new plugs be bad. My Opti is a 2000 and it has never seen anything but 10% oxy and Amsoil HP. Besides the bad plugs only other is water pumps every 2 years. Opti`s are bad about water pumps they do not last long.

    5

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