On 26 July 1887, he defeated Richard Long in a seventh round knockout at the Opera House in Wellington, New Zealand.

[2] He defended the title successfully on 23 June and 1 July 1888 against Joe Molloy and Edward Jones in two fifth round knockouts.

In a fourth round knockout, he defeated Jim Saxon in another New Zealand Lightweight Title match on 1 September 1888.

[2] In his first fight in America, he defeated Johnny Griffin, an exceptionally talented featherweight, in a third round knockout at the California Club in San Francisco on 12 July 1889.

In an important bout on 30 July 1889, he fought a twenty-seven round draw against English champion Frank Murphy in what was billed as a World 120 pound title match.

Murphey immediately unloaded a serious right as Weir landed, known as the "torpedo punch", which resulted in a knockdown that ended the bout after a count of ten.

Weir successfully used his clever ducking and bobbing as a defense in the fight, avoiding Murphy's powerful right which had plagued him in their earlier title bout.

However, Australia and New Zealand continued to recognise his title until he lost to Albert Griffiths known as Young Griffo in Sydney on 2 September 1890.

[9] He would lose to Young Griffo again on 22 July 1891 at the Sydney Amateur Athletic Club in another World Featherweight Title match.

[2] On 31 May 1892, he fought Johnny Murphy in San Francisco in a forty round no contest bout that was billed as a 122 pound World Championship.

On 28 December 1892, in San Francisco, he had a rematch with Tommy White, whom he had defeated two years earlier, that ended in an epic thirty-four round no contest.

[10] In an unusual match on 16 December 1893, in Paterson, New Jersey, with George Dixon, Murphy was disqualified in the third round for a blow to the referee.

[13] On 26 November 1898, he was knocked out by a rising Chicago star, Eddie Santry, who would take the World Featherweight Championship, according to most sources, the following year against English boxer Ben Jordan.

Murphy's knockout loss to Santry took place in the fourth round at the Commercial Athletic Club in St. Louis, Missouri.