By weigh-in time today, challenger Mike Weaver had hardly uttered a word since he signed three weeks ago to fight Larry Holmes on Friday night for the World Boxing Council version of the heavy-weight championship in Madison Square Garden.

Weaver weighed 202 pounds to Holmes' 215. The champion tried to get a rise out of the challenger with some taunts at the scales, but it turned out to be the quietest ceremony since Muhammad Ali left the boxing scene.

Weaver was so up-tight that an insider wondered if he might not be tipped over and knocked out by Holmes' first flurry of solid punches.

"He's stiff as a board . . . scared," the insider said. "And he says he doesn't like crowds. What is he going to do if those Latins from Spanish Harlem come down to see Roberto Duran and Carlos Palomino and fill the place?"

An observer at the prefight physical examinations on Monday said Weaver did nothing but laugh in response to questions.

"The atmosphere was strained as Holmes and Weaver sat on the same examination table," the observer reported. "Holmes said to Weaver, 'Don't laugh - I'm going to knock you out in four rounds.Look at him - he's scared stiff.'

"Holmes said to Weaver's manager (Don Manual), 'You got a million dollars? I'll bet you a million I'll knock him out in four rounds.' The manager said, 'I'll try to get the million.'"

Weaver has won 20 of 28 bouts, 14 by knockouts, and in a ghosted article in the New York Post entitled, "Why I'll Beat Larry Holmes," it was noted that the challenger stopped his last five opponents with the reminder, "A lot of guys have scored big upsets to win the championship."

Among those five knockout victims were onetime prospects Stan Ward and Bernardo Mercado. Holmes is making the third defense of his title but has yet to win acceptance, despite being unbeaten in 30 bouts, with 21 knockouts.

Weaver figures to be a tuneup for Holmes before the champion takes on Earnie Shavers Sept. 14.

The three major television networks rejected the Holmes-Weaver bout as a mismatch and it will be seen on Home Box Office cable television in Arlington, Va., and other cities, and in some cities on closed-circuit television. The advance sale for the live fight at the Garden has been slow, compounding the fear of a Holmes-Weaver debacle.

Former welterweight champion Palomio is supposed to get the first shot at Sugar Ray Leonard, if Leonard takes Wilfredo Benitez's title on Dec. 1, provided of course that Palomino wins here Friday against former lightweight champion Duran in their nontitle bout.

Mike Baker, U.S. junior middle-weight champion from Arlington, Va. (35-8-1, with 20 knockouts) meets Clarence Gilmore of Memphis (9-4) in a preliminary.