PORTLAND – Prime Motor Group, which has five auto dealerships in Maine, is buying the Clair Motors dealerships in Maine, New Hampshire and Massachusetts.

The purchase was made final this week for an undisclosed price and will give Prime a total of 15 dealerships in the three states.

The Clair dealerships came on the market after the recent death of the company’s founder.

The company has more than 500 employees, including about 200 who already were working for Prime.

Workers were scheduled to change Clair signs to the Prime brand on Wednesday at Ford, Lincoln-Mercury, Mazda, Volkswagen and Honda stores in Saco, as well as the Clair Collision Center.

Prime’s expansion in Maine, which began almost three years ago, is driven by Ira Rosenberg, who owned nine dealerships in Massachusetts and came out of retirement to build a network in Maine.

Rosenberg’s purchase of the 43-year-old Clair operation underscores his regional ambitions.

“We intend to make it one of the largest dealers in New England,” he said.

Before buying Clair, Prime hired a business broker to locate dealerships that were for sale, according to David Rosenberg.

The Rosenbergs and James Clair’s four sons had longtime business friendships, he said.

“With the dealerships they have,” he said, “they could have sold to anyone.”

Other Maine dealers said they were aware the sale was pending.

“It’s more of a Boston feel, a Boston style,” said Adam Lee, president of Lee Auto Malls. “It’s a little more aggressive. Some people are OK with that.”

Lee has a Honda store in Auburn and will be watchful of Prime’s purchase of the Honda franchise in Saco.

“I’m not thrilled at having Ira as a Honda dealer,” Lee said. “He’s a very good dealer and a very good competitor.”