Merc 525SC belt gear ratio
 

I need to know the stock belt gear ratio Merc uses on the 525SC. I think the upper pulley is 3.55", but I can't find the size of the lower pulley. I need it to run desktop dyno.
Thanks!

The gear ratio as stated in my Merc manual is 2:1. I think the top is 3.25 and the bottom is 6.5, never measured mine though and the manual does not give diameters of the pullies. Stock boost is listed at 5.5 lbs.

Keep in mind that the stock comp ratio is only 7.5:1.

Thanks Griff!