With Akash Gill having returned home with his Canadian Under 19 team and Ross Kinnerley restricted to just batting, Tech's remaining bowlers all suffered, with Trent Hemi (2-49) the only one who didn't have a mess made of his figures.
It got no better in the batting department as Ross Kinnerley (28) opened and looked to attack quickly, but promptly lost brother Fraser and was then caught, while Akhil Kumar fell the next ball as Dinwiddie (4-59) struck back from the early pounding to take out the top order.
Dominic Lock (22) started the recovery but was soon Dinwiddie's third victim, and from 70-5 in the 11th over the writing was on the wall.
Tech would struggle through another ten overs, losing wickets throughout as Dinwiddie, Engelbrecht (4-21) and Thomas Redpath (2-16) cleaned up Sam Suri, Quinn Mailman, Hemi and Chris Friedel in single figures, while Sam Roebuck (17) and Tyler Lock (11 not out) put up short resistance.
At Wereroa Domain, the fifth-placed home side completed a comfortable seven wicket win over eight-placed Wanganui Collegiate 1st XI, who entered the second half of the summer without several departed senior students.
Collegiate raised a competitive 240, being bowled out in the last over, with Bruce Donald (82) anchoring the new look top order, with support coming from Charlie Greatbatch (24), Shaun O'Leary (31) and Henry Kilmister (31).
Experianced Matt Good (4-33) took wickets at both ends of the innings, while Adam Simonsen (2-38) got the key wicket of Donald and Chris Petersen (2-57) and Carl Trask (2-43) took middle order scalps.
Good completed all-but a perfect match when he opened Wereroa's innings and raised 97 in 85 balls before being caught off Joseph Abernathy in sight of his century.
Simonsen (64) partnered him to led their team to 162 by the 23rd over, with Collegiate ultimately trying nine players at the bowling crease to little success.
It was a cruise from Good's dismissal as Thomas Morgan (44) carried on before being caught only five runs from victory, which came in just the 37th over.
Scoreboard
Marist 343-8 (J McIlraith 84, C Stewart 71, M Fraser 49, A Dinwiddie 44, Z O'Keeffee 24, N O'Leary 23no; T Hemi 2-49, C Friedel 2-59, S Suri 2-75) bt Tech 117 (R Kinnerley 28, D Lock 22; A Dinwiddie 4-59, Z Engelbrecht 4-21, T Redpath 2-16) by 226 runs.
Collegiate 240 (B Donald 82, H Kilmister 31, S O'Leary 31, C Greatbatch 24; M Good 4-33, A Simonsen 2-38, C Trask 2-43, C Petersen 2-57) lost to Wereroa 244-3 (M Good 97, A Simonsen 64, T Morgan 44) by seven wickets.