** This is not an official answer, I may be wrong.
With OCI/PIO card, you can stay in India as long as you want. There was a rule after every 180 days, you need to register in local Police Station about extension of your stay, however since 2014 (with Modi Govt) they abolished the rule. However I dont have much idea about Tourist visa requirements for overstay.
Me/My wife(Malaysian citizen and Indian PIO card holder) traveled to India in 2013, we did overstay of little over 180 days, while returning back to the US, we were questioned and fined. Luckily we were little early at the airport, that we did not miss our flight for questioning and fine process.
I would suggest check all resources online, if needed apply for OCI/PIO card. OCI/PIO card mostly does not have overstay limitations.