Bekko Page got Poverty Bay off to a flying start with three consecutive boundaries in the opening over and hit five in all in his 29 off 20 balls.
Fifth man in Charlie Whitfield (18) shared a 69-run partnership with McInnes, but no one else scored in double figures.
Hudson Clarke picked up 4-30 off 7.3 overs, including bowling McInnes to end the game held in sweltering conditions.
McInnes’ performance was the second-highest knock of the day, bettered only by Northland opening batsman Tommy Litchfield’s 73 off 64 balls (12 fours, one six) in a seven-wicket win over Northern Districts Māori.
The U19 tournament runs to Friday and features eight districts – Poverty Bay, Hamilton, Bay of Plenty Coastlands, BoP Lakelands, Counties-Manukau, Northland, ND Māori and Waikato Valley.
Rounds 1 to 3 are 50-over games, followed by four T20s.
SCOREBOARD
Northern Districts Rangatahi Emerging Tane (Under-19) tournament, at Harry Barker Reserve
Hamilton 193 all-out in 41.2 overs (Kieran Nolan 50, Angus Spelman 34, Hudson Clarke 31; Johnathon Gray 2-12-6, Jonah Reynolds 2-32-7.2 overs, Caleb Taewa 2-33-7) def Poverty Bay 140 all-out in 28.3 overs (Patrick McInnes 71, Charlie Whitfield 18; Hudson Clarke 4-30-7.3, Chris Pradeep 3-16-4, Oliver Penfold 2-23-4) by 53 runs.
Bay of Plenty Coastlands 159-3 in 33.2 overs (Nihar Parmar 63 not out, Harrison Miles 25, Sam Cross 24; Harshil Jain 1-15-4, Chainvir Singh 1-21-6) def Counties-Manukau 156 all-out in 44.5 overs (Harkamalpreet Singh 41, Akaldeep Lahory 29, Prabhsimhran Singh Jawanda 20; Nihar Pramar 3-12-7, Rico Adsett 3-16-6, Aarish Aryal 2-6-2.5 overs) by 7 wickets.
Northland 134-3 in 26 overs (Tommy Litchfield 73, Zac Laing 27 no; Caleb De Bruin 1-9-4, Josh Waller 1-24-5) def Northern Districts Maori 133 all-out in 42.5 overs (Shima Fletcher 33, De Bruin 29; Owen Prinsloo 3-26-7, Dailyn Dickeson 2-18-6, Campbell Soanes 2-31-10) by 7 wickets.
Waikato Valley 120-5 in 25.4 overs (Josh Hart 47, Logan Hickey 35) def Bay of Plenty Lakelands 116 all-out in 46.5 overs (Ryan Lloyd 21, Lucas Neill 19; Connor Banks 19; Jacob Hagoort 3-16-9, Josh Hart 2-10-5) by 5 wickets.
Poverty Bay Premier Grade 40-over Doleman Cup, round 6
Bollywood High School Old Boys 157-7 in 34 overs (Taye McGuinness 70, Connor Starck 21, Alex Shanks 20; Harvey Reynolds 2-3-3, Daniel Stewart 2-29-8, Matt Cook 2-32-7) def Coastal Concrete Old Boys Rugby 156 all-out in 32.5 overs (Harvey Reynolds 29; Connor Starck 3-18-6.5, Uday Charlee 3-20-3, Riker Rolls 2-28-8, Tharuka Fernando 2-36-6) by 3 wickets.
Gisborne Boys’ High School 1st XI 159 all-out in 38.4 overs (Patrick McInnes 47, Steve Whitaker 39 no, Caleb Taewa 26; Gautam Sareen 2-16-5, Simarjit Singh Basra 2-25-8) def Moshim’s Spice Horouta Te Waka 157 all-out in 37.2 overs (Simarjit Singh Basra 46, Gautam Sareen 23, Himanshu Bhargav 20; Caleb Taewa 4-47-8, Patrick McInnes 3-16-7, Brandon Fearnley 2-27-7.2) by 2 runs.
Points: HSOB 18, GBHS 14, Horouta 8, OBR 8.
HSOB to play GBHS in final on Saturday
Poverty Bay Reserve Grade T20, round 6
Moshim’s Spice Horouta Te Waka Presidents 150-5 (Tony Bucheler 43, Matthew Kotuhi 43; Cody McMurray 2-11-4, Callum McInnes 1-16-3) def Gisborne Boys’ High Second XI 78-9 (William Edginton 24; Clarence Campbell 2-8-2) by 72 runs.
Bollywood HSOB Presidents 140-4 in 19.2 overs (Jak Rowe 32, Brad Reynolds 32, Jonny Hardie 29no, Ollie Needham 21; Anish Shivdikar 3-11-4) def Pioneer Ngatapa Green Caps 137-5 (Ollie Jonasen 45, Brent Gallagher 32; Jak Rowe 3-13-4) by 6 wickets.
Points: HSOB 20, Ngatapa 20, Horouta 4, GBHS 4.
HSOB to play Ngatapa in final on Saturday