Six different goalscorers were on the scoresheet for Ian Sampson's side including new signing Shaun Harrad, who took just 11 minutes to find the net for his new club, levelling Crewe's early opener.
From then on it was one-way traffic as Northampton moved to within seven points of the play-offs thanks to further strikes from Jacobs, Beckwith, Holt, Osman and McKay.
Expectations will now be raised for the visit of struggling Barnet to Sixfields on Saturday as the Cobblers look to maintain their momentum.