Washington lightweight Darryll Tyson may have been as nasty as he wanted to be, but unsung Julio Guerrero was tougher than anyone thought he could be.

Bouncing back from each and every wicked flurry heavily favored Tyson had to offer, the steadfast Guerrero survived seven rounds on gumption alone before his corner surrendered last night in front of a surprised 1,300 at Washington Convention Center.

Tyson (33-4, 16 knockouts), the North American Boxing Federation champion, was at times tentative, but more often resembled that boxer with the same surname. He scored with vicious connections that stunned Guerrero (11-15-1).

"He was determined for me not to knock him out," Tyson said. "He hung in there like a journeyman should."

Guerrero refused to fold, his performance reaching at times amazing levels in the punishment he withstood. Sometimes pinned against the ropes or trapped in a corner, the Puerto Rican fighter showed resiliency that few expected.

At 1:51 of Round 7, Guerrero's cornermen threw in the towel -- literally -- to halt the bout.

Robert "Boo Boo" Sawyer, who has not fought since 1986 and trained with former world champion Hector Camacho for a year during his comeback, sent Marvin Ladson collapsing backward with a sharp right to score a knockout 25 seconds into Round 2.

Charles Tuttle, 30, a dumptruck driver from Bowie, came back after nine years. A moment of hilarity was Keith King's undoing, as he missed a dead-straight right, stumbled toward Tuttle, dove and banged his head -- hard -- against the corner post. He did not return for Round 3.

District junior bantamweight Mark Johnson's fight against Wayne Johnson (no relation) proved quick and painless -- for the former, at least, who looked chagrined after the ringside physician did not allow him to return for the second round after the punishment he received.

District junior middleweight Gerry Payne scored a six-round split decision over Richmond's Timothy Knight.

A pair of local fighters won their pro debuts. Tyrone Washington, a lightweight from Capitol Heights, beat Christopher Moore with a second-round technical knockout and Curtis Peoples stopped Dominick Ross at 1:43 of the first round.