Plan to stay 4 days at Catalina island, taking the Catalina express from the Newport Beach, where can I park my car for the 4 days? What are the options?

The Catalina Flyer (not the Catalina Express) departs from Newport Beach. We recommend parking in the Balboa Pier Parking Lot, also known as the Balboa Municipal Lot. It is located on Palm Street, out on the oceanfront. You can park up to seven days, and costs $23.25 per 24 hour period at the time of this post. Parking can be paid for in advance at https://balboapierlot.clickandpark.com/ , however pre-payment does not reserve you a spot. NT

You can park your car in an overnight garage, but it's about 30 bucks a day, but not sure if Catalina Express validates. Catalina Flyer does though.

To reserve parking you can go to balboapierlot.com. The rates vary depending on the time of year you travel. You may also want to check the website for the city of Newport Beach. Their fees are likely cheaper than the Balboa Pier Lot. Their website is newportbeachca.gov. Enjoy Catalina!

I parked in the street but not sure overnight is allowed. There is a lot nearby with daily rates. Check "Catalina Express" site for details or links. Another option is to find free, or low cost lot and then take an Uber/Lyft/taxi to boat dock.