Below is some info for out of state like myself. It really doesn't specify if that is 90 days per year or not. I have a PA boaters card.
Out-of-state residents who are at least 16 years of age and who will be in New Jersey for less than 90 days may operate a power vessel on the waters of the State of New Jersey if they possess a certificate issued by their state of residence or if they have in their possession written proof of successful completion of a boating safety course approved by another state, the US Coast Guard, or the National Association of State Boating Law Administrators (NASBLA).