Step 1: Understanding the Concept:
India's coastline has two sides, the western coast facing the Arabian Sea and the eastern coast facing the Bay of Bengal, and each side has its own set of major ports.
Step 2: Sort the given ports by coast.
Mumbai (Maharashtra), Kandla (Gujarat) and Kochi (Kerala) all sit on the Arabian Sea side, so they are western coast ports. Chennai, however, is in Tamil Nadu on the Bay of Bengal side, making it an eastern coast port.
Step 3: Why the other options are wrong (as answers to 'not on west coast').
Mumbai, Kandla and Kochi are genuinely on the west coast, so picking any of them would be incorrect for a question asking which one is NOT there.
Final Answer:
Chennai is the port that is not on India's western coast.\[ \boxed{\text{Chennai}} \]