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.