Harvard's trip to Colorado springs and the NCAA hockey championships go on the line tonight when the Crimson faces Clarkson in the semifinal game of the ECAC tournament at 6:45 p.m. at the Boston Garden.

If Harvard defeats Clarkson, it advances to finals Saturday when it will meet the winner of tonight's B.U.-Cornell confrontation. The winner of the tournament automatically goes to the NCAA tournament, and the other entry is chosen by a committee of coaches.

Assures Honor

The runner-up is usually the nominee for the second position, which means that a Harvard victory tonight would virtually assure the Crimson of the honor.

But first the Crimson must defeat Clarkson. In their two previous meetings this year, the teams have each won a game. Harvard won an easy 7-2 victory in the first game, but the Golden Knights evened the score four days later with a 4-2 win at their rink--whose peculiar dimensions always baffle visiting teams.

Overtime Victory

Harvard's spirits should be improved after its dramatic overtime victory over New Hampshire. The Crimson's only weak spot should be George McManama, who is still nursing an injured shoulder. But the first line center played the entire game Tuesday, and set up Bobby Bauer's winning goal. Defenseman Chris Gurry also has a slight pulled muscle in his leg, but he should be able to play, according to coach Cooney Weiland.

Clarkson's 19-5-1 record is surprisingly good for such a young team. Coach Len Ceglarski skates 13 sophomores and his captain, defenseman Wayne Lachance, is a junior.

Golden Knights

Tonight the Golden Knights may not have the services of injured first-line wing Bill O' Flaherty, who only played a few minutes in the B.C. contest Tom Reynolds will fill his position, joining center Tom Deacon and wing Alf Laki.

The second trio is sparked by high scorer Rick Magnusson, who centers the line for wings John Halme and Luc St. Jean, Gerry Ladouceur, Terry Ainslie, and Greg Lewis skate on the third line.

Clarkson also has one weak line at defense. Paul Davidson, who teams with Fred Erickson on the second defense, has the flu and may not play. If he is out, Ceglarski will only use the first team of Lachance, Keith MacLean, and Erickson.

Bruce Bullock, who has been outstanding all season, will be in the nets for the Knights.