Apprentice Beau Mertens maintains his narrow lead in the Melbourne jockeys' premiership after a winning double at Flemington but he has also faced questions from stewards over one of his rides.

Mertens went into Saturday one win ahead of Craig Williams in the premiership and both riders claimed two wins apiece.

Mertens won on Schism and Cannyescent to take his season tally of metropolitan victories in Victoria to 66.

Williams won aboard Charlevoix and Ability and remains one behind as he chases a sixth premiership.

Stewards also questioned Mertens over his tactics on fourth placegetter Hot Ruby in the David Bourke Provincial Plate (1600m), particularly early in the race and early in the home straight.

However, they accepted the jockey's explanation after taking into account the instructions from trainer Luke Oliver and the sectionals of the race.

"It probably looks like she is dashing home but on my feel it was only grinding home," Mertens told stewards.