Yes, you can join the Merchant Navy even if your 12th PCM percentage is 63%, but it depends on the course and institute you are applying to. For most DNS  and BSc Nautical Science programs, the minimum requirement is usually 60% in PCM and 50% in English, so you meet the basic eligibility. However, some top institutes and sponsorship programs may have higher cutoffs, so make sure to check the specific eligibility criteria of the institute you're interested in. Also, you’ll need to qualify in the IMU CET exam and meet the medical fitness standards as per DG Shipping norms.