If you overstay your tourist visa even by 1 day, you will be held at the airport and be required to pay a fee to be allowed to depart India. 

Not only will you be fined but this will result in a lot of problems if you plan to visit India for a second time.

We recommend that you ensure you plan your trip so your eVisa fully covers the period of your visit. More information here: https://www.ivisa.com/india-visa-application