Just replaced my 13/19 stock with a used 14/21 I picked up here I did notice the clearance from impeller to wear ring was more then my stock. (Stock clearance .008") (used 14/21 .013") anyway I noticed what seemed like cavitation off the hole my top speed decreased by 2-3mph. My rpm was one noch lower then with the 14/21 mabe it's too much prop I wonder if a 14/20 would still be too much? Does any one use a 14/21 with good results? Is .013" clearance too much clearance? What kind of clearance would be best .003?