Northern Pirates shattered a 17-year premiership drought in Illawarra baseball with an emotional 8-5 win over Dapto Chiefs in Saturday's grand final.

The third-placed Pirates beat reigning premiers Wests Cardinals and minor premiers Chiefs in successive weeks to claim their first championship since 1997.

Pirates made history by claiming the second and third grade titles on Saturday plus the fourth grade premiership on Sunday.

It was the first time the 'Bucs had won the top four grade titles, while their fifth grade side was beaten in the preliminary final.

In first grade, Brenden Lower followed his match-winning pitching effort against Cards with another brilliant nine-innings display, fending off several Chiefs threats in the late innings.

Lower gave up just seven hits, five earned runs and struck out seven batters, including two in the ninth.

Pirates outhit Chiefs 14-7, with skipper Andrew Clifford, Lachlan Maher and Jesse Lynch all going 3/5.

Lynch clinched a memorable family double, with his father, Ken, the MVP in Pirates' last premiership triumph.

A month of rain helped Chiefs qualify for the grand final courtesy of a washout but ultimately the five weeks off between games hurt the competition's top side.

Although on their home diamond, Hector Harvey Park, Chiefs were rusty early on and with Lower virtually untouchable, Pirates led 5-0 after five digs.

Chiefs scored three runs in the sixth to make it 5-3, before Pirates hit back with a run in the top of the eighth to extend their lead to 6-3.

Chiefs rallied again with two runs in the bottom of the eighth to only trail 6-5 and, with men on base, were threatening.

But with two out, a relay throw from Pirates right-fielder Brad Drain to first baseman Clifford and onto catcher Luke Rich threw out Mark D'Antonio at home plate.

Afterwards both skippers said the play at home base was a turning point.

"They would have tied it up but for great work by Brad and then Luke," Clifford said.

"They were coming hard but we held firm and that was a bit of a story of the match.

"We led and they came back but we managed to keep our noses in front."

Chiefs skipper Craig Leighton said it was one of a couple of "massive mistakes" which cost his side.

"Baseball's a game of momentum and we had it and lost it right there. Even at 6-5 down with a man on third the pressure was still back on them. Instead the inning was over and a big chance was gone."

Pirates scored two more runs in the ninth to lead 8-5, before Lower struck out the first two batters and induced a meek ground ball to short stop Maher to seal victory.

"It's the biggest day of my life," Clifford said in a jubilant Pirates dug-out.

"I started here in '98, the year after our last premiership as a 15-year-old and 17 years later I can finally celebrate a premiership.

"It's a huge day for everyone, we are one very proud club."

Pirates beat Cardinals 7-3 in second grade and 8-6 in third grade, while Pirates beat Warriors 16-6 in fourth grade.

Warriors are fifth grade champions after beating Cardinals 16-10.