Winning possession from Anthony Grant just inside the Southend half in the 28th minute, Racon powered forward and unleashed a 25-yard drive into the top left-hand corner that left goalkeeper Rhys Evans a helpless spectator.
It was a goal out of character from the rest of the match which had plenty of endeavour but produced very little to set the pulse racing.
Despite the trickery of Charlton's Kyel Reid on the left flank, and the occasional forays from midfield by Southend's Josh Simpson, too many moves broke down on the edge of the box.
The result was that neither goalkeeper had much to do, but Charlton's Rob Elliot was the busier of the two.
Before Racon struck, Elliot had to deal with speculative long-range efforts from Blair Sturrock and Simpson, but his one important save came 10 minutes after the break, when he dived to his right to turn away a close-range effort from Sturrock.
Soon afterwards Peter Gilbert powered an effort just wide of the Charlton post, but just before the end it needed a fingertip save from Evans to prevent Johnnie Jackson from increasing the visitors' lead with a well-struck free-kick.