Floyd Mayweather -- 'I've Made a Lot of Money Off Johnny Football'

Floyd Mayweather Jr. says it's about time he partied with Johnny Manziel ... because he made a TON OF CASH gambling on the former Texas A&M superstar over the years.

Mayweather was out in L.A. last night and talked about the huge celeb party at Justin Bieber's Bev Hills pad earlier this week ... where the cops rolled up to handle a noise complaint.

"We love the LAPD," Floyd said ... "They came to do they job to make sure we were in good hands."

As for Mayweather's betting habits -- back in September, the boxer put down $300,000 on Johnny and the Aggies to beat Arkansas ... and THEY DID!!!! Cha-CHING!!

Least Floyd could do is buy Johnny a beer, right???