Sydney will meet Randwick-Petersham in the First Grade Limited-Overs Cup grand final after both recorded comfortable semi-final wins on Sunday.

An undefeated Beau McClintock century underpinned Sydney's 35-run victory over St George at Drummoyne Oval, while the Randy Petes crushed Manly-Warringah at Manly Oval.

The Tigers will be shooting for their second one-day title in three seasons when they host Randwick-Petersham in the decider next Sunday at Drummoyne.

The visitors, who last won the title in 2011/12, will go in as outsiders but showed in the win over Manly they will not be easily discarded.

Randwick-Petersham was 3-38 and 6-108 before Riley Ayre (106) produced a defiant knock to repel Manly and help his side reach 213 from their 50 overs.

The total still looked a little light on but would prove to be more than enough, with the Waratahs crumbling to be all out 128.

Ayre's three wickets guaranteed him man-of-the-match status, with Ryan Ninan also chipping in with three scalps.

"It's always tough defending anything under 240 against a quality opposition, but Riley Ayre showed his class, as he has all season, and our bowlers were incredible," skipper Jason Sangha said. 

"It was an amazing win and I am very proud of their efforts."

McClintock belted five fours and three sixes in his brilliant 96-ball knock to put Sydney firmly in control against Saints.

Set 290 to win, the Dragons started in positive fashion and were 2-154 before losing 8-100 as Sydney quick Nic Bills (5-44) stepped up to run through the middle and late order.

The first day of Premier Cricket's round 13 was washed out due to heavy rain on Saturday.

All 10 matches will be played next Saturday, as one-day limited-overs matches (50 overs per side).