Fifties from John Matchett and Jason van der Merwe led CIYMS to a 174-run victory over Muckamore at Moylena on Saturday.
Batting at five, van der Merwe (82) hit his third league half-century of the season - striking six fours and four sixes against his former club.
Matchett posted 58 off 80 balls – hitting seven fours and a six in the process.
He looked in fine touch as he scored his second 50 in succession, following on from his 73 against Waringstown last weekend.
Muckamore professional Fahad Iqbal got the wicket of Matchett as he played on to his stumps.
Nigel Jones (47) fell just short of his half-century as he gave spinner Craig Drummond his only wicket of the afternoon by hitting a ball straight to Iqbal.
Jones faced 44 balls and hit four fours and two sixes.
The opening two partnerships (52 and 68) put CIYMS in a great position as they were 120 for two in the 25th over.
Wicketkeeper-batsman Chris Dougherty gave Ashwin Shetty his first wicket, finding the safe hands of Shane Henderson as he departed for 28.
Ryan Hunter also scored 28 and Matt McGillivray was run out for 29 to leave the Belmont side 226 for five in the 43rd over.
A partnership of 73 between van der Merwe and Jacob Mulder propelled CIYMS to 299 for six in the last over before they finished their innings on 314 for six.
Shetty was the pick of the Muckamore bowlers with two for 93 off his 10 overs.
The tally of 314 proved a huge total at Muckamore. Normally 250 is a safe score given the nature of the pitches, so the hosts were going to be up against it from the start.
They were always behind the rate and didn’t get off to the best of starts as opener Aditya Adey was out for a golden duck, having been caught at slip by Jones off the bowling of Allen Coulter.
Two for one soon became 12 for two as Iqbal (6) slapped a Jones delivery to David Robinson.
The CIYMS bowling attack kept things tight and made it tough to score runs.
Sam Gordon then gave his wicket away as he was caught by van der Merwe to give Jones his second wicket of the match.
A partnership of 33 was established between Adam McDaid and Drummond before the former played a Trevor Britton ball onto his stumps to depart for six.
This left his side on 36 for three.
Drummond went on to top-score for Muckamore with his 34 before he was caught down the leg-side by Dougherty off the bowling of Matchett.
Jamie Magowan, Luke Allen, Arnold Oduvelil, Henderson and Shetty all failed to reach double figures as Neil Gill finished unbeaten on 23.
Jones returned the best CIYMS figures as he claimed two for 14.
CIYMS remain top of the Robinson Service Premier League – four points clear of Waringstown – with a game in hand.
Their next assignment is a trip to CSNI next week.