I have a 2014 50HP 4S and it's been faultless. Like others have said, there's a difference between Chinese Made & Chinese Manufactured.
Mercury have tight quality control over their process and parts.
The 40/50/60 is an inline 4 cylinder that runs smoothly and has more torque than other 3 cylinder motors of the same HP.
Would I buy another one? Without any hesitation based on my current 3 years of ownership.