Gary Williams, American University's basketball coach four years, yesterday accepted an offer to coach at Boston College. He will replace Tom Davis, who left last week to coach at Stanford.

Williams, who the last two seasons led American to its first back-to-back 20-victory records and postseason tournament bids, was an assistant to Davis at Boston College in 1977-78 and before that at Lafayette. His record at AU was 72-42.

"This is a great opportunity for me and my family and I had to take advantage of it since it was offered," Williams said. Boston College scheduled a press conference today to introduce Williams.

He was one of seven coaches interviewed Saturday and Sunday, including Jim Lynam, former American and St. Joseph's coach now an assistant for the Portland Trail Blazers, and Lou Campanelli, coach at James Madison.

Bob Frailey, AU's director of athletics, said the search for Williams' replacement will start immediately and will be done "as quickly and efficiently as time will allow. I don't have any names right now." Asked how he felt about losing Williams, Frailey replied, "Terrible. He's a super kid and he'll do well."

Among likely candidates to replace Williams are Ed Tapscott, his top assistant who knows the present team and local recruiting well; Brad Greenberg, an assistant coach at St. Joseph's who once played and was an assistant coach at American, and Joe Boylan and Art Perry, assistant coaches at Rutgers. All have either coached or played at American under Williams, Lynam or Tom Young, the Eagles' last three coaches.

It could not be ascertained last night whether Wil Jones, an AU alumnus who coached the University of the District of Columbia to the NCAA Division II championship, will apply for the job. He was a finalist when Williams was hired. Another head coach with local experience and roots is Billy Jones, now at the University of Maryland-Baltimore County.

The new coach will inherit all the players from a team that was 21-9 last season, losing to eventual champion Bradley in the first round of the National Invitation Tournament.

"It's a tough thing to leave with the players we have returning. That's the toughest part," said Williams. "You like the friends that you make. I was very happy with the players. I enjoyed coaching here and I like the Washington area.

"But Boston has its attractions. It's a little like Washington. Certainly the Big East (Conference) is an attraction. Boston College is a good school."

There, Williams will take over a basketball program that is known nationally. This year's team was 21-9 and advanced to the final eight of the NCAA tournament.

Williams would not comment on his income, but Davis was earning $70,000-$80,000 at BC. Sources said Williams' three-year contract calls for a salary in the $45,000 range and that he will be able to have a basketball camp.

"The first thing I've got to do is meet the team up there and then get on the road recruiting," he said. April 14 is the national signing date for college basketball recruits.

Before accepting the job, Williams had turned down Duquesne and Seton Hall. Yesterday, Seton Hall picked Peter J. Carlesimo, coach at Wagner College. He replaces Hoddy Mahon, a Seton Hall assistant who became interim coach when Bill Raftery resigned five months ago.