Gai Waterhouse will have two runners in the Melbourne Cup with Excess Knowledge winning his way into the field - twice.

The $4.40 favourite in Saturday's Lexus Stakes (2500m) at Flemington, Excess Knowledge was in a battle in the final 200m with the Darren Weir-trained Zanteca ($13).

Excess Knowledge won by a short half-head with Zanteca's rider Damian Lane immediately firing in a protest against Dwayne Dunn, saying he had come in on top of his mare and impeded her running.

However, stewards disagreed, saying at no time did Zanteca lose her running and they would be reluctant to uphold such an objection.

Even though a Melbourne Cup start was on the line, neither Waterhouse, who won the Cup with Fiorente two years ago, nor Weir showed any tension as they waited for the result.

"Isn't it exciting," Waterhouse said.

She was also excited once it was clear the horse would join stablemate The Offer in the 24-horse field for Tuesday's Cup.

"I'm confident he will go well," she said.

"He's so well weighted in the Cup."

Excess Knowledge will carry his 51kg Cup weight with handicapper Greg Carpenter saying he he would not get a penalty for the narrow win.

Kerrin McEvoy is his likely rider.

The United States, who was No.24 for the Cup before Excess Knowledge won the Lexus, still gets a run with his owner Lloyd Williams taking stablemate Amralah out on Saturday.