Boatsetter has implemented a search algorithm that determines where your boat is placed in the rankings. The higher the ranking, the more inquiries you will receive. Things like being responsive, approving or declining bookings, receiving positive reviews, having your boat set as instant bookable, etc. will help your boat get to the #1 position.
You can attract renters to your listing by letting your friends, colleagues, and neighbors know that they can now easily and safely rent your boat. Once your listing is live, you should promote it on any of your social networks (Facebook, Twitter, CraigsList, LinkedIn, etc). The more people who know your boat is available, the more likely it is to be rented!
You can read more about the search algorithm by following this link.