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Thread: 2012 Mercury 40hp efi

  1. #1
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    Default 2012 Mercury 40hp efi

    I got a 4 stroke Mercury 40 hp big foot looking for mods to do on its , i check around and the 40 hp 4 cylinders and the 50hp and 60hp are the same parts number except one restriction plate in the air passage, i took it off rand better more low end torque, but if i run more then 5200rpm it go to safe mode and drop to 3000rpm and i get a message from vesselview saying (mass airflow calculation is above limits) is my map sensor is Broken ?
    I was thinking that efi engine if you put more air the ecm will recalculate and adjust the air fuel mixture.
    Or i just swap for a 60hp ECM.

  2. #2
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    I suspect it's seeing pressure at rpms that aren't expected with a 40. How many coils do you have? I think they switched back to the 2 coil system in 2011. I have a 50 ecm but it's from a 4 coil motor. Don't know if it matters but I wouldn't bank on it being the same. If you're near Panama City, FL you're more than welcome to try.

    As far as more power, you can mill the head and swap the cam. Not a ton of improvement to be had in the ports but there's some transitions that can be smoothed.

    Good luck,

    Jim
    Cracker Bay Thundercats

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    I got 2 coils and I live In Quebec Canada kind of far from you.
    changing cam or internal parts I will wait for the warranty to run out before i ding in the engine

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    Yeah, that's a haul from here. Try some nitrous.

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