Hello KKG

It's very difficult to tell you about how much marks to score because the seat is reserved according to the rank.Rank depends not only on the score but also the level of paper,no. of students giving exams and many more.Hence,it's not possible to say the marks to get a seat in IIT Bombay in any branch,you need atleast a rank of around 2400,the last being for metallurgy branch.For more details ,you can visit https://engineering.careers360.com/exams/jee-advanced

Good Luck!