At the 2002 Commonwealth Games, Manswell won the silver medal, losing the gold to Canadian Jason Douglas.

Manswell again won silver at the 2002 Central American and Caribbean Games, losing final to Victor Bisbal.

At the 2003 Pan Am Games Manswell beat American Devin Vargas in the semifinals, but lost in the final to Cuban Odlanier Solis 3 to 15, giving him yet another silver medal.

Manswell turned pro in 2004 at age 27 and beat his first 20 opponents, including Louis Monaco.

In 2011 Manswell lost three fights in a row; first KO'd by Bermane Stiverne, then outpointed by undefeated Mike Perez and fringe contender Cedric Boswell.