you are not eligible in merchant navy after 10th
but you can do this after completing your intermediate with physics,chemistry,mathematics as your subjects
you age should be between 16.5 to 19.5
you should score minimum of 60% in intermediate.
Here are the best Merchant Navy Institutes in India:
Training Ship Chanakya, Navi Mumbai.
Marine Engineering & Research Institute (MERI), Kolkata.
Marine Engineering & Research Institute (MERI), Mumbai
Lal Bahadur Shastri College of advanced Maritime Studies and Research, Mumbai .
Try your level best.