The tardy sister of the city's new commuter ferry program will begin service on Monday, just in time for a week of fare-free travel, officials confirmed.

The Rachel Marie has been certified by the Coast Guard for operations in Hawaiian waters, after arriving here a week later than her twin vessel, the Melissa Ann.

The service, dubbed TheBoat, was launched on Sept. 17.

The 72-foot aluminum catamarans will make a total of three daily trips in each direction between Kalaeloa and Aloha Tower.

Each vessel can carry up to 149 passengers. Most morning trips have averaged about 50, but the 4:20 p.m. trip from Aloha Tower carried 127 — the highest number so far.

Fares will be suspended on TheBoat and five connecting bus lines next week in an effort to attract more passengers.

"We're really excited to move ahead with the second vessel and the fare-free service next week," city spokesman Bill Brennan said. "We hope that people will at least give TheBoat a try during that week. The people who are taking TheBoat regularly seem to be really enjoying it, and to enjoy having that option."

Regular fares on TheBoat are the same as for TheBus. The one-way fare for adults is $2. Bus passes are also honored on TheBoat.

The ferry demonstration project is expected to continue for at least one year. Federal grants totaling $5 million are to pay for the ferries, and the city is spending $1 million to run the special buses.

For more information, go to www.trytheboat.com.