As you Marantz 6025 is a belt drive type turntable, the most possible problem is that the belt has been cut or destroyed. You can check it out before order a new one.
Here is the replacement procedure. Pull up the rubber mat, pull up the platter and find the belt. If the belt is removed from the platter, replace it with the glossy side outward. Pull the platter back at the original position. Turn until one of the 2 big openings come over the motor pulley. With your finger place the belt from the platter at the motor pulley. Pull the rubber mat back. You are ready. Here is a schematic for all the above:
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