The Australian Maritime Safety Authority said it received a distress beacon alert about midday on Monday from the 19-metre-long yacht known as the Spirit of Mateship.
A mechanical failure - believed to be a broken rudder - saw the ship become stranded around 185km east of Nowra, but it has since drifted further east to sit around 300km off shore.
Navy vessel HMAS Canberra is assisting in the rescue effort, as is NSW Police vessel Nemesis.
But 50-70km/h winds along with up to six-metre seas has made executing the rescue effort challenging for crews.
Australian Maritime Safety Authority duty manager Ben Flight said the yacht should be rescued by Tuesday afternoon at the latest.
"It's still time sensitive, they've suffered a mechanical failure, and they can't make their own way at the moment, and are taking on water," he told Seven.
"With the conditions as they are, it is quite a challenging environment, If they can't recover the crew this morning, the weather is forecast to ease through the day, so hopefully they'll be able to do that later in the day."
Mr Flight said the two people on board the boat were believed to be uninjured, but presumably exhausted.
They would be airlifted out of their vessel but for the choppy conditions, he said.
"Unfortunately due to the weather it's unsafe to winch and recover someone into a helicopter,so we're hoping they'll be able to recover them via a sea boat," he said.
"Once they're on board a vessel, they'll make an assessment of the two crew and then determine the best way to get them back to land as safely and as quickly as possible.
Two Royal Australian Navy ships and an RAAF C-130J Hercules aircraft were initially involved in the rescue operation.
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