Lightly raced mare River Delta has claimed a valuable stakes win in the Black Pearl Classic at Geelong despite jockey Brad Rawiller returning to scale overweight.

The Peter Moody-trained mare scored by a half head in the Listed race for fillies and mares on Wednesday's Geelong Cup program.

Rawiller weighed in 1kg over and stewards issued the jockey a severe reprimand, having established that the girth strap had been changed when the horse was saddled up.

Moody said it was an important victory for River Delta, the $3.50 favourite, who has always shown talent but has been resticted to five starts for four wins.

"She's a good mare that has always shown us very good promise but we've had to be patient," Moody said.

"She's had a few little issues along the way."

The four-year-old daughter of Al Maher was first-up and overcame a wide barrier to defeat Danestroem with Nadeem Lass a half neck away third.