I purchased a used Martin Cougar Magnum compound bow. The number on the bow is CLXM 31173-3 I am new to the archery game. Could you please let me know how, if possible I can adjust the percentage of let off
That depends entirly on the cam. On some Martin cams a simple module change will change let off. On others it may not be so simple. It is going to be difficult (like guessing your weight over the net difficult ) to answer if you can't identify the cam
You've got an '83 model Cougar Magnum. It should be equipped with round wheels that each have two axle bushings. The bushing closest to the outside perimeter offers 50% let-off, the other 30%....hey, these weren't high let-off days! Anyway, changinf from one to the other required swapping wheels end to end (upper wheel to lower limb) and reinstalling the axles in the opposite hole.
Hope that helps.