Onchan surprised Ayre United in the GH Corlett Woods Cup preliminary round.
Craig Marsh, Mark Burman, Gerard Colligon and Mark Rees were on target in a 4-2 home win.
Phil Quayle and Elliot Cureton replied for the Tangerines.
Douglas Athletic are up to fifth in JCK Division Two after an 8-1 thrashing of Braddan.
A Josh Green treble, a Liam Dawson double and further goals from Darren Shields, Andy Newton and Stuart Monks (penalty) secured the three points to lift them above Colby in the table.
MGP rider suffered 'neck and chest injuries' following crash in practice
Mauro Poncini fatally injured at Cruickshanks Corner
Sidecars to return to Isle of Man TT Races in 2027
Three-year commitment to class announced
Inquest opens into death of local MGP rider
Sam Naughton fatally injured in incident at Doran's Bend
Nickolas Ellis to make Silverstone sportscar debut
Manx driver entering penultimate round of Ligier European Series