Bespectacled Kothari was given good support by leg spinner Sarvesh Lokegaonkar (2-5) and medium-pacer Jayesh Mhatre (2-24) as the winners grabbed five points with an outright win.
Phadkar XI overcame a first innings deficit of 14-runs, scored 178 in the second to set a 164-run target for opponents at the Sachivalaya Gymkhana ground.
Rangnekar XI captain Ramanpreet Singh, batting at number four, showed the way with a composed 51 off 91 balls (6 fours) but his teammates lost their way and were shot out for 139.
In another match, openers Kushal Dhavane (79) and Sachin Yadav (66) came together in a 112 runs stand, supported by Karan Naidu (53 not out) to swell Vijay Manjrekar XI second innings score to 277-8 at stumps in a drawn first round tie against Vijay Merchant XI.
Brief scores
Dattu Phadkar XI 142 & 178 all out (Pratik Manjrekar 35, Kunal Gawand 53; Sagar Mishra 4-41) beat Khandu Rangnekar XI 156 & 139 all out (Ramanpreet Singh 51; Karsh Kothari 5-30, Sarvesh Lokegaonkar 2-5, Jayesh Mhatre 2-24). Points: Phadkar (five points). Rangnekar (zero).
Vijay Manjrekar XI 157 & 277-8 (Kushal Dhavane 79, Sachin Yadav 66, Karan Naidu 53 no; Atul Singh 3-69) drew with Vijay Merchant XI 267-8 decl. Points: Merchant (three), Manjrekar (one).