If you are 12th pass and very bright in studies then this may not be a career for you as you have plenty of opportunities away from sea. But for an average student this career can prove better alternative.
If you are Engineering graduate from I.I.T./ other similar prestigeous engineering colleges / government engineering colleges then I will definitely ask you to think it over again before joining merchant Navy. If you want to go abroad for studies or want to settle abroad then this career is not a good option.
For average students or graduates from private engineering colleges, this option is better than any other field as that is highly competative. Here there is no competition. You clear your exams and will be promoted in due course. After about 7 to 10 years, you can be promoted as Chief Engineer whose everage salary starts at USD 8,000/-