Australians will skipper all three boats in SailGP's $US1 million, winner-take-all season championship race after Nathan Outteridge earned the final spot with his Team Japan crew.

Outteridge had finishes of sixth, second and first aboard his fast, foiling 50-foot catamaran on San Francisco Bay on Saturday to join defending champion Tom Slingsby of Team Australia and Jimmy Spithill (Team USA) in the grand finale on Sunday (Monday AEDT).

The three Aussies will first need to keep their boats intact in Sunday's two fleet races that precede the $US1 million race.

Slingsby capsized his boat, the Flying Roo, in practice on Thursday, causing major damage to the wing sail that forced the shore crew to work through two sleepless nights to repair. Spithill rolled his $US7 million catamaran on Monday.

Team Australia had finishes of 2-4-3 on Saturday while Team USA went 5-7-5. Those crews came into this regatta already assured a spot in the million dollar race.

While Slingsby looked strong two days after his capsize, Spithill struggled with his starts and will have to do better on Sunday to win the boatload of cash.

It left Outteridge and Slingsby are tied at 18 points in the lead for the San Francisco regatta championship.

"We did a great job today," said Outteridge, an Olympic gold and silver medallist.

"Tom was out there sailing well today, but tomorrow's a different story. I'm sure Jimmy will come back strong. We've just got to get through those two races tomorrow.

"That will be the No. goal, to try and win the San Francisco event and then back it up with the overall season victory."

"All in all, we're happy and we're heading into tomorrow sort of in the hunt and we've still got a boat that's working, so that's a good thing," said Slingsby, an Olympic gold medallist.

"For me, there's not really any psychology to it. Nathan just sailed a little better than us today, a little cleaner, a few less mistakes," Slingsby said. "Good on them. But for us, we know that if we sail as well as we know we can, we're very hard to beat."

Spithill said the Americans need to get to the championship race intact "and then put the throttle down."

Slingsby couldn't resist zinging Spithill, who has tried to play up his role as underdog to Australia and Japan.

"I've heard on the grapevine that the USA team is trying new things, but if I was them, I would cancel those plans and get back to what they know, because they didn't look too good," Slingsby said.

Slingsby beat Outteridge for the inaugural season championship and $US1 million prize in 2019. SailGP expanded the grand finale to three boats for the pandemic-delayed second season.