Walk Behind Clutch problem

I bought a Scag hydro 52" used this year. I am having a problem with it cutting. I changed the blade engage switch because I thought that might be the problem. I usally use a Turf Tiger but got this because I need two mowers on some big property's. I unloaded it today and it cut for about 10 minutes and the blades quit turning. You can pull the switch to engage the blades and nothing. If you try it tomorrow it might work. Is it a bad clutch? Could the mower not be putting out enough voltage to engage the clutch? Could it be getting damp and making the clutch slip?
Thanks

What is the battery voltage with the engine running at 1/2 throttle or more? disconnect the power connector to the clutch and with an Ohmmeter, check the electrical coil in the clutch and from each leg to ground. Most clutch coils have 3.2-3.9 Ohms and should be no continuity (open circuit) from each leg to ground.
Mad Mackie in CT

Thanks I will check that. Do you know what the voltage is supposed to be with it running?

With a fully charged battery, the voltage at the battery should be 13.9-14.3 VDC with the engine running at half throttle or more.
Mad Mackie in CT