During his amateur career, Welin represented clubs in Västerås such as BK Rapid, Stockholm's IF Linnéa, and Malmö's GAK Enighet.
He grew up in Carazinho in the southern part of the country (the state of Rio Grande do Sul), where his Swedish-born father, Gunnar Welin, managed a large agricultural business.
That same year, Welin also became the Swedish champion after knocking out Säffle boxer Conny Olausson in the final on February 27 in Stockholm.
Welin made his European Championship debut in May and won his first match against a Polish boxer but was then knocked out by Mujo Bajrovic from Yugoslavia.
While in the then-turbulent Moscow, Welin defeated a boxer from Japan and a Ghanaian but lost a close quarter-final match to American Raul Marquez.
[1] The year 1991 started well as Welin repeated his Swedish Championship victory by knocking out a Småland boxer in the final on February 25.
Welin won four more matches against modest opposition in the United States before suffering his first defeat by technical knockout against Ugandan Richard Okumu in London.
During 1995, Welin fought five matches (four wins and one loss); among other victories, he knocked out Pori boxer Joni Nyman in Helsinki.