The T.C. Williams girls lightweight eight defeated Washington-Lee by two lengths yesterday to capture its third straight national title in the 49th annual Scholastic Rowing Association championships. A crowd of nearly 3,000 watched at Lake Occoquan.

Williams' girls junior eight, Yorktown's girls junior four and Washington-Lee's boys lightweight four also won championships against 40 of the nation's strongest rowing schools.

Crews from Philadelphia and New Jersey won 11 of the 25 championship events. Holy Spirit of Absecon, N.J., won four championships, while Winter Park, Fla., won three.

In the boys varsity eights, Holy Spirit edged St. Andrews, Del., by six seats in 4:25.7 for 1,500 meters. Williams, the best local crew, finished fourth, just 6.3 seconds behind the winner, in its best time of the season. St. Andrews and Liverpool, Ohio, finished one-two in the girls varsity eight, while Yorktown held off W-L and Williams for third. The Titans had been expected to vie for the title, but finished fifth.

The Titans' lightweight victory was particularly impressive because of several personnel changes that could have disrupted the crew's cohesiveness.

"We had one girl quit and lost another to mononucleosis earlier in the season," said stroke Edie Goodyear. "It was just 2 1/2 weeks ago that we got our new seventh seat (freshman Laura Machanic) from the third eight, but we all hung together and worked that much harder."

Undefeated Williams used a powerful "starting 20" stroke to jump to an early four-seat lead that widened to one length with 500 meters remaining.

"We sprinted the last 150 yards and pulled away," said sixth-seat Becky Arington. "We've worked hard on our sprints and it really paid off today."

This was the final scholastic race for six of the Titan oarswomen. Bow Nikki Parry, Elaine Powell, Sarah Berg, Arington, Goodyear and coxswain Barbara Alicea will graduate in several weeks, leaving only Kris Armstrong and Katie Bair to defend the title. Machanic will transfer to boarding school next year.

In the girls junior eights race, Williams used a secret signal to confuse rival shells.

"We had a really good start, but whenever we felt anyone closing on us we took a 10," said sophomore coxwain Melissa Goldblatt. "But instead of calling out the stroke change, we used a special signal. I just said 'now' so the other crews couldn't tell what we were doing."

The Titans, who were undefeated against junior competition, finished the 1,500-meter course in 5:20.7 to beat Belleville, N.J., by more than two lengths.

In the girls junior fours race, Yorktown held off Winter Park and Williams for a four-seat victory. The Titans missed second place by a half-second.

W-L was the only area boys crew to win a championship as it outlasted Edgewater, Fla., and Upper Merion, Pa., to win by three seats in 5:19.2.