Remy Gordon opened the scoring after 10 minutes, before two goals in three minutes, one of which a Marsden penalty, gave the Yachtsmen a 3-0 lead after 23 minutes.
Marsden then got his second of the game to cement the victory, before a 67th minute Billy Smith penalty and a Jacob Joyce strike in the dying moments proved to be nothing more than mere consolations for the hosts.
The Yachtsmen had the game won halfway through the first half, allowing them to take their feet off the gas for much of the second half in what will be a pleasing performance for manager Pawel Guziejko.
Wroxham got off to the perfect start, Sam Harty making a determined burst through the PNS midfield after 10 minutes, before laying the ball to Remy Gordon who coolly slotted it into the far corner past Lee Crockett.
The Yachtsmen were enjoying good periods of possession, with their lower league opponents struggling to keep up with their quick movement of the ball.
This pressure paid off soon after as the visitors bagged two goals in the space of three minutes.
Joe Marsden coolly converted his second penalty of the season after 20 minutes, sending the ‘keeper the wrong way after Gordon was pulled back by Crockett after charging down his attempted clearance.
Ross Durrant then dispatched a wonderful right footed strike from the edge of the box three minutes later, the ball clipping the post on its way into the far right corner for 3-0.
Centre back pairing Rio Starkings and Matthew Halliday were marshalling Peterborough’s attack well, limiting them to various half chances as the half wore on.
Cruickshank in the Wroxham goal was forced to make a good save from a Billy Smith free kick just before the break, tipping the ball round the post in Peterborough’s most meaningful attempt of the half.
The start of the second half then saw both the good and the bad of the Wroxham goalkeeper.
A fine save from another Smith effort was followed by a missed catch from a cross seconds later, Nick Davey completely missing the headed chance from three yards to let him off the hook.
Marsden then claimed his second of the game as Wroxham made it 4-0, Crockett in the PNS goal reeling on the floor after a fine block from a Cook effort, which allowed the right back to smash into the vacant goal from 18 yards.
The referee then awarded his second penalty of the game, this time to the home side, as Sam Groves was penalised for handball with Smith converting the resulting spot kick after 67 minutes.
This seemed to spur the hosts on, with Jason Kilbride on the PNS right wing causing numerous problems down the Wroxham left.
And it was a ball from the right that provided PNS with their second goal in the dying moments of the game, Jacob Joyce firing in from 12 yards to make it 4-2, but it was too little too late as Wroxham held out for the victory.
The Yachstmen will now face St Neots in the next round on the 14th September.
Report by Thomas Crabb