Af92mpe125u58 furnace starts up and runs fine until the blower kicks on then it blows the main 15amp fuse. So what should I look for or just got ahead replace blower motor?

Could be the motor but, make sure the start/run capacitor is good. Sometimes a bad capacitor will cause the breaker to trip because the motor draws a lot of startup current. Could also be a weak breaker. Breakers are $4-10, capacitors about the same. Cheaper than a motor!