Amtrak’s Downeaster continues to suffer delays and cancellations well into the busy summer tourism season, frustrating passengers and officials who manage the train service.

Some trains from Boston this week are ending and starting the trip in Wells, and the rail authority is busing passengers between Brunswick and Wells and between Portland and Wells. Some trains are not stopping in Saco and Old Orchard Beach.

The rail authority said Monday that it will be two weeks before the service can operate on a normal schedule and without delays.

A long-anticipated tie replacement project is the source of the Downeaster’s problems.

The Northern New England Passenger Rail Authority and Pan Am Railways, the freight railroad company that owns the track between Portland and Plaistow, New Hampshire, have been replacing 30,000 rail ties on the 78-mile line. Pan Am replaced 8,000 ties last year and 22,000 this year.

The “tie gang” – the Pan Am crew that removes the old ties and replaces them with new ones – did not began working this year until late May. It started work in New Hampshire and moved north. The rail authority announced Monday on the Downeaster’s website that crews have reached Portland and that all ties have been replaced.

However, it will take two weeks before trains are legally allowed to run at normal speeds, according to the announcement. That’s because current speed restrictions on parts of the line can’t be lifted until a number of trains roll over the areas with the new ties, said Wayne Davis, who heads Train Riders/Northeast, a rail advocacy group.

Also, a “track geometry car,” equipped with lasers to measure the curvature and alignment of the track, must go over it and take measurements, he said, and crews will have to make adjustments.

In June, some trains were arriving in Brunswick more than three hours late. Now, trains are arriving 30 minutes to one hour late, Davis said. He said passengers have had “terrible” train service in recent months.

“We had been hoping to have it all fixed so when the tourists arrive they would have been spared all this,” he said.

The tie replacement project has been delayed by a number of factors, including the Amtrak derailment May 12 in Philadelphia, which forced Amtrak to delay sending heavy machinery equipment to Maine, and the mechanical failure of some equipment, said Martin Eisenstein, chairman of the rail authority’s board of directors.

“There were circumstances beyond our control, and hopefully they won’t happen again,” he said.

He said the rail authority has been frustrated by the delays.

The authority bought the ties for $2.3 million, and Pan Am is paying for the equipment and labor to install them.

A list of schedule changes can be found at amtrakdowneaster.com.

The service offers five daily round trips between Boston and Portland and two daily round trips between Boston and Brunswick.