A pau hana cruise from Aloha Tower to Kalaeloa has quickly become the most popular daily trip on TheBoat, the city's new commuter ferry system.

The 4:20 p.m. voyage has consistently attracted the most passengers since TheBoat was launched two weeks ago, and was filled to capacity on Wednesday for the first time.

In fact, 15 would-be passengers were turned away after the ferry reached its legal limit of 149, city transportation director Melvin Kaku said.

The city has a policy of leaving no ferry riders marooned, so the 15 were offered rides on a special express bus, he said.

Free wireless Internet service will be available on TheBoat starting today, city spokesman Bill Brennan said.

TheBoat offered free trips all week in a promotional effort meant to attract customers, but it remains to be seen whether the numbers will remain high when fares are required next week. The regular cost of a one-way trip is $2 for adults. Bus passes are also honored.

The 4:20 p.m. trip has been popular since the beginning, carrying 101 passengers on the first day of service, and from 66 to 149 on every other weekday, Kaku said.

All other trips have carried 72 passengers or fewer, and have generally averaged 40 to 50.

Ridership and passenger preferences are being monitored during the one-year ferry demonstration project so officials will know whether changes are needed for the service to continue, he said.

But no specific ridership benchmark has been set to determine whether the program is successful, he said.

Federal grants totaling $5 million are paying for the ferries, and the city is spending an additional $1 million to operate five new bus routes linked to the piers.

The two ferries in the system are now running well — after one, the Rachel Marie, suffered a mechanical problem that scuttled her maiden voyage Monday morning.

That vessel has older, weaker engines and travels a few knots slower than her sister vessel, the Melissa Ann, which began service a week earlier, said Kaku.

The Melissa Ann makes the Kalaeloa-Aloha Tower run in about 45 minutes, while the Rachel Marie averages 10 minutes longer, he said.

Reach Johnny Brannon at jbrannon@honoluluadvertiser.com.