When the boys with their bottles and blondes return to the stadium next fall, Harvard will have a new defensive line coach stomping the sidelines, but no one yet knows who he'll be.

Bowdoin College announced yesterday that Harvard's present line coach, James C. Lentz, has been named head coach of football and lacrosse. He'll assume his duties on September 1, when Bowdoin begins football practice.

Harvard's football coach, John M. Yovicsin, said yesterday that Lentz's appointment had been "in the wind for two or three weeks," but he has not selected a replacement. "I have a lot of things on my mind, but nothing definite," he said.

Lentz has been a coaching assistant to Yovicsin for 16 years, eleven at Harvard and five at Gettysburg College. The Crimson coach said that "Harvard has played extremely successfully defensively under Jim Lentz."

Described as a "very good organizer and a fine teacher" by Yovicsin, Lentz graduated from Gettysburg in 1951, where he captained the football team. After two years as freshman coach, Lentz moved up to the varsity staff to work with Yovicsin. The two have been together ever since.

Lentz will replace Bowdoin's Pete Kosty, who resigned a month ago to become associate head coach at Wesleyan. Bowdoin's sports information director, Joe Kamin, would not specify how many men were considered for the position, but he said there were "very many."