Hello aspirant,
I am here for helping you.
Yes, you definitely can join merchant navy with this age and qualifications which you mentioned here
Read the following guidelines for having a gist of eligible criteria to join merchant navy.
1:   the minimum age is 17 year and the maximum age is 25 year to be eligible for examination pertaining to the merchant navy. As per the government rules, the maximum age relaxation for SC and ST is 5 year.
Physical fitness is of outmost importance for a career at sea.

2: Education qualifications : the minimum eligibility for courses in nautical science and marine engineering is 10+2 or an equivalent examination with physics, chemistry and mathematics.
I hope it will help you..
For more queries you can upvote me and can ask in the comment box.
Best of luck.

To join merchant navy and eligible for government pertaining examinations, one must between age of 17 to 25 years. Following courses are to join merchant navy after 12th:-

• To join as deck officer

1. BSc nautical science (3 years)

2.Diploma in Nautical Science (Leads to a BSc Nautical Science. Duration is 1 year)

To join as an engineer, you need degree of nautical engineer.(4 years)

To join as a ratora class after 10th or 12th, you need pre sea GP rating course of 6 months.

If you want to join in catering deptt. After 12th then theu have to pursue either of:-

1. Maritime catering course(6 months)

2.BSc in marine catering (3 years)