Merchant Navy Officer

Hi Staish,
The process is through an entrance test. You must score at least 50% to be eligible. Interview and medical tests are also to be cleared before you are selected, but it will vary from institute to institute. Ideally, you need to complete a Bachelor's degree in nautical science or marine engineering to become a merchant navy.
However, you can also gain direct admission after class 12th PCM to join as deck cadets. For direct entry as deck cadet, you must undergo a basic pre-sea training.
I hope it helps.

JEE score is not used by admission in Merchant Navy colleges. If you want to join Merchant Navy, you are advised to appear for JAT conducted by Indian Maritime University. JEE score will be used by Indian Navy for selection in technical branch first time this year. Without historical data, it's difficult to predict what JEE score will be required for selection in Indian Navy in 2017.

Hello Ranajit,
As physics and mathematics are important for doing engineering in marine, as you said you want to do it after 12th, you will not get a higher post on deck. My suggestion is to join any merchant navy school as they will teach you for 6 months and then make you to go on training.