'Real public service is not about you. . . . It's about sacrifice.'

One spring day when he was 18, Ed Flynn left school, went to a South Boston recruiting station, and signed up for the Navy. A quiet boy who wasn't into sports the way his father had been, Flynn idolized the veterans he knew as a boy. They had made sacrifices for their country. He could think of nothing more honorable.

Without telling his parents, he went alone and put his name down for boot camp. ''It was my life," he said recently. ''It was what I wanted to do."

A reservist who has never seen combat, he has spent much of his working life in office and teaching jobs. Only in the last few years has he volunteered for missions that have lasted for months at a stretch.

But the military, he says, became the defining force of his life. In it, he has found friendship, professional confidence, and a chance to lead.

Now on the campaign trail for an at-large seat on the City Council, Flynn is using his military service as a way to stand out in a field of young, ambitious political newcomers. In a race in which his opponents are scrambling to appeal to the so-called New Boston, Flynn presents himself as a candidate of the old school. He speaks about patriotism and the need to help the working class, the people who built Boston, he says, and the people who are struggling to stay here.

His campaign signs announce ''Democrat-Veteran," once an almost universal tagline on Boston political signs, but rarely seen in the post-Vietnam era. While his opponents squabble over how to attract young professionals to the city, Flynn is devoting much of his attention to aging veterans and proposing tax breaks to help longtime residents remain in the city.

''Eddie wants to protect the heart and soul of Boston," said his college roommate, Roger Oliveira, who spends his weekends passing out Flynn's campaign literature.

On the campaign trail, Flynn, 37, has been inevitably compared to his father, Raymond L. Flynn, Boston's mayor from 1984 to 1993. The physical resemblance is striking, but they seem to be of different makes. Ed, the younger of two sons, seemed to go out of his way to avoid the limelight as a boy, whereas his gregarious father developed a following as a star high school athlete.

''He's very quiet; it's hard to get any information out of him," Ray Flynn said of his son. ''It's a different kind of circle that he travels than I did as a kid. Mine was all about sports, couldn't get enough of it. Eddie's satisfied sitting in the back of church and not trying to get recognized, not trying to make any kind of appearance."

As a teenager, Ed Flynn shunned the glitzier perks of being the mayor's son, like box seats at the Superbowl, his father said. But the younger Flynn vividly remembers attending the 1981 dedication of the first Vietnam memorial in the country at M Street Park. Among his childhood heroes was his father's brother, a Vietnam veteran who included his nephew in the small circle he spoke with about his war experiences.

''The reason I went into the military was because of those young guys that made a sacrifice," Flynn said. ''And I'm not putting myself in their category, certainly. They're the real heroes."

Trained as a communications specialist, Flynn, now a petty officer first class, writes news releases, handles communications between Navy ships and ports, gives tours of vessels, and participates in terrorism response drills. He was a reservist from 1987 to 1993 and from 1998 to the present. In 2001, he decided to make a more intensive commitment by volunteering for active duty. In the past few years, he has sometimes spent months at a time on missions around the world.

His wife, Kristen, said his love of the military consumes even his free time. When the Navy sent him to Washington, D.C., to help with President Bush's inaugural last year, he would spend hours on the weekends visiting wounded veterans. When they travel, she said, he has her take his picture next to statues of war heroes.

''His face just lights up; that's just what he loves," she said. ''He's not into tanks and weaponry. He's into the human story, the story of the guy who left his family and went to serve in Vietnam."

As a reservist, he will probably return to full-time service in the next year, even if he is elected, which could mean months away from Boston. Yet Flynn considers his military experience an asset that would outweigh his potential absence. ''I have life experience that I learned mostly in the military that I think could be helpful to Boston," he said.

As a campaigner, Flynn combines a sober, methodical demeanor with his father's grass-roots politicking. He has no website. He spends much of his time shaking hands at MBTA stops.

Flynn's platform includes proposals for a $15 or $16 an hour city minimum wage, city-funded vouchers for private school, property tax abatements for veterans, the elderly, and long-time residents.

He is also a vocal critic of Mayor Thomas M. Menino, charging that Menino has failed to address crime. Flynn believes that the city should offer substance abuse treatment on demand, which springs from his helping his older brother, Ray Jr., struggle with depression and substance abuse.

Flynn benefits from being his father's son and a native of South Boston, among the city's highest-turnout neighborhoods. But the city's electorate has changed drastically since his father left the mayor's office, and Flynn has had difficulty raising money. He mostly campaigns alone.

''Running for office is not public service," he said recently over a hot chocolate at a diner near Dudley Station, taking a break from greeting voters on a blustery afternoon. ''I think real public service is not about you. It's about your country, and it's about sacrifice."