The mower turns on fine but when i engage the pto to start mowing it doesn't work and shuts off and blows the fuse

Could have bad pyo switch or pto clutch.make sure every thing turns freely,blades and pullys then unplug clutch and try to enguage if does not blow fuse check clutch with meter. put meter on ohms probe one terminal and other on ground via clutch housing should not have continuety check other terminal to ground.voltage goes in one term and out the other like litebulb if potting (insulator) in clutch is melted wire inside will short on housing.hope this helps