Excelled as an athlete in high school, setting school records in track and field and starring in football.
Received a college football scholarship offer, but was recruited to the Marine Corps and joined the Armed Forces at the age of 17.
Weaver started boxing when he was in the United States Marine Corps from 1968 to 1971. He was encouraged to start boxing after he floored the Camp Lejeune heavyweight champion with a single punch during and argument over which song to play on a jukebox. Weaver won the All-Marine title and the All-Services title before going on to the national Golden Gloves and AAU tournaments and the Pan Am Trials.
Toiled as a sparring partner for former world champion Ken Norton, who discouraged him from retiring on three different occasions.
Ken Norton gave Weaver the nickname "Hercules" when Weaver was working as a sparring partner for Norton.
Weaver's professional career got off to a slow start. He lost 3 of his first 4 fights and was 6-6 after 12 fights.
Faced a turning point in his career when manager Dan Manuel, who had heard that Weaver had dropped rugged Boseman Jones in a sparring session, introduced himself and took charge of the heavyweight's career.
Was convinced by Manuel and Ken Norton that he could become more than just a tough opponent and began to train with conviction.
Kayoed the hard-hitting Bernardo Mercado and then on January 18, 1979, Weaver knocked out Stan Ward in nine rounds to win the USBA heavyweight title.
Weaver then fought Larry Holmes for the WBC heavyweight title on June 22, 1979. Earned worldwide respect by extending Holmes to the 12th round before being kayoed by a desperation right uppercut...Had Holmes hurt in several rounds and gave the champion his roughest defense to that date.
Captured the WBA's number-one ranking by outboxing Scott LeDoux over 12 one-sided rounds in November of 1979.
Entered the ring a heavy underdog against undefeated WBA champion John Tate on March 31, 1980. Behind on points and needing a miracle kayo to take the title, Weaver registered one of the most shocking knockouts in boxing history with 45 seconds remaining in the bout, catching Tate with one of the most classic left hooks in boxing history to win the WBA heavyweight title.
Weaver made his first title defense against Gerrie Coetzee in South Africa on October 25, 1980. In a very tough fight, Weaver retained the title with a thirteenth-round knockout.
Weaver had a tentative agreement to meet Gerry Cooney on October 22, 1981, but the WBA said Weaver had to fight James "Quick" Tillis next or be stripped of the title. Cooney was ranked #1 by the WBA and Tillis was ranked #3, but the organization said Tillis was the highest ranked contender when Weaver was due for a mandatory defense in March 1981. Weaver defeated Tillis by a fifteen-round unanimous decision.
Weaver was scheduled to fight Randall (Tex) Cobb several times in 1982, but the fight failed to happen because of injuries to Cobb.
Michael Dokes took the title from Weaver with a controversial first-round TKO on December 10, 1982. They had a rematch on May 20, 1983, and Dokes retained the title with a fifteen-round draw.
Weaver fought Pinklon Thomas for the WBC heavyweight title on June 15, 1985, and was knocked out in the eighth round.
Weaver's last fight was on November 17, 2000. At the age of 49, Weaver took the bout on short notice and fought a rematch with 51-year-old Larry Holmes and was knocked out in the sixth round.
Valued his close-knit family and adopted their deep belief in Christianity.
"Finally in the fifteenth round, my manager reminded me I was telling everyone I knew that I was going to knock Tate out. He told me I was running out of time and it was now or never so you better do it! I sat in my corner and recited the 23rd Psalm to myself and asked the Lord to give me the strength to knock him out. He gave me more than I needed."