From donations averaging $25 or $50 each, the fund Marine Lt. Col. Oliver L. North's U.S. Naval Academy buddies established to help pay his legal bills has grown to an estimated $130,000.

Mark Treanor, one of the trustees of the Oliver North Legal Assistance Fund, said he has not counted contributions that arrived yesterday, but estimated them at $30,000, augmenting the $100,000 reported in the fund on Thursday.

He attributes the boost in donations to North's televised appearance this week before the Senate and House select committees investigating the Iran-contra affair. "People are seeing he's not this bad guy he's reported to be," Treanor said.

"He's a straight arrow, an honest individual. As a friend and on a personal level, I would trust him totally."

North, he said, "has been very gratified, not only by the fact that funds have been contributed but also because he has received tens of thousands of letters in support."

Stacks of telegrams awaited North when he arrived to testify yesterday. And thousands of persons have telephoned government and news media offices supporting the Marine officer who was fired from the National Security Council staff last November.

Many of the messages appeared to be from political conservatives and from military veterans, and while encouraging North, they criticized the congressional investigating committees in harsh terms.

"Your courage stands out like a beacon against the lesser men who would like to bring you down," wrote one well-wisher from Pacific Palisades, Calif.

"Don't let the committee get you down. It's easy to be in their position," a telegram from Nashville said.

Mary Longa, an assistant at NBC News in Washington, said her office had received about 12 calls an hour in support of North. "We are getting two different sorts of calls: A lot of people are wanting to know where to send money; others just say they want to express support for Ollie."

George Vinson, deputy director of the Senate's telephone exchange, said operators handling incoming calls for the House and Senate found Thursday's volume much heavier than usual. The operators usually handle 20,000 calls daily, but he said he had no count for Thursday's volume.

Gregg Takayama, press secretary to Senate panel Chairman Daniel K. Inouye (D-Hawaii), said his office has received 200 to 300 calls each day of North's testimony, compared with the usual 100 calls a day.

The calls started out running 80 percent for North, but Takayama said that since Wednesday night, they have been running at a 50-50 rate for North and the two committees.

At the White House, spokesman Marlin Fitzwater said operators handled more than 2,000 calls Wednesday and Thursday, with all but 80 supporting North.