Hello Jaywant,

In order to apply for the Merchant Navy,

the minimum requirements are that you should have a minimum of 60 percentile in Science Stream.

Also, you need to clear the physical and entrance exam that is conducted.

for more details, there is a detailed article mentioned our website::

https://university.careers360.com/articles/merchant-navy

Hello,

After class 12, you are eligible to study the following merchant navy courses:

• B.Sc. Nautical Science
• B.E. Marine Engineering
• B.E. Naval Architecture and Offshore Engineering
• B.E. Petroleum Engineering
• B.E. Mechanical Engineering
• B.E. Harbour & Ocean Engineering
• B.E. Civil Engineering
• B.E. Electrical & Electronics Engineering
• B.Sc. Marine Catering
• Electro Technical Officer Course

To get more information  please go through the following link 

http://www.indiaeducation.net/careercenter/professional-courses/merchant-navy/

Hope this helps ......