Recently shut the motor off and it wouldnt start, found no spark. Bought an aftermarket coil, installed it and fired right up and ran for about 2 minutes, shut it off and no spark. Returned it got another coil, installed it ran fine. Mowed on 2 different occasions over the course of 2 weeks. Mowed this past weekend for 2 hours shutting it off once and it wouldnt start, no spark again.

Could it be the aftermarket coil? Or something else?

Thanks

Sounds as though the problem could be the ignition switch or related wiring. You said it would not start only after shutting it off. That seems to eliminate the safety switches. Locate the wire that is connected to the coil (kill wire) and the next time it fails to start disconnect this wire and see if it will start. This wire is routed through the ignition switch and all of the safety switches. And is looking for any chasis ground which will shut the engine off andit will not re-start until this ground is removed. If you find the fault here, your old coil may be okay.

Just go ahead and take the kill wire off..... (kill the engine by popping the plug wire off)
Aftermarket coils are not to be trusted either.... not up to the same standard as oem.