A damaged city commuter ferry is expected to be back in service tomorrow morning after a rebuilt diesel engine was installed over the past few days.

The drydocked vessel, known as the Rachel Marie, should be placed back in the water and receive a Coast Guard inspection over the weekend, ferry project manager Darin Mar said.

Prospective riders should check the ferry Web site, www.trytheboat.com, before tomorrow morning for the latest update, he said.

The vessel, one of two 72-foot catamarans that sail between Kalaeloa and Aloha Tower, has been idle since its port engine failed on Nov. 8.

The problem forced the cancellation of two of the ferry program's six daily trips in each direction. The city has operated shuttle buses to make up for the canceled trips.

"We knew there was potential for mechanical and weather issues causing no-sail conditions," Mar said. "That's why buses are built in as a backup."

The boat broke down after a cooling system failed, which allowed coolant to mix with engine oil and caused the pistons to seize inside the cylinders and bend the engine's crankshaft, he said.

The city and ferry contractor Hornblower Marine Services are considering having a spare engine shipped here in case it is needed later, Mar said.

The ferry program, dubbed TheBoat, has carried more than 12,000 passengers since it was launched in September for a one-year pilot project. Some crossings have carried more than 100 people, but others have been nearly empty.

"This is still a very early stage of the project, so it's hard to draw any type of conclusion whatsoever in terms of ridership and the long-term future of the project," Mar said. "Ridership numbers won't have too much meaning just yet."

The ferry service and five linked bus routes are expected to cost $6 million for one year. Federal grants are providing $5 million.

Mayor Mufi Hannemann announced that from Dec. 3 to 14, TheBoat will accept Toys for Tots donations of new, unwrapped toys from riders.

In return, TheBoat will give each donor a ticket good for either a future ride on TheBoat, including the F-shuttle buses, or a beverage and a snack item on TheBoat.

The city also will have a Toys for Tots collection box in the Honolulu Hale courtyard through Dec. 16 for donors viewing the Honolulu City Lights displays.