Belmont finished 8-222 before bowling SKLP out for 104.
Standouts with the bat included Lewis (61) and Tirmazi (48), with Brooks (2-20) and Kavanagh (2-21) the best of the bowlers.
Belmont Second Grade went down to Bayswater, being all out for 130 in a disappointing day.
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Martin (51) was the top scorer but without support, neither he nor Jokich (2-28) could hold back Bayswater, which finished 6-176.
It was a tight game between Fifth Grade Belmont and Karrinyup, who may meet again in the finals.
Belmont will be hoping for a different result as, despite the efforts of Goes (63), Osborne (58) and Tobias (26) they were all out for 182.
Bowlers McAullay (2-22), Patel (2-24) and Kavanagh (2-32) couldn’t hold back the tide as Karrinyup pipped them with 8-183.