Not good. Curry would beat him clearly. Floyd at 147 doesnt have the power to keep Curry off him, therefore he wouldnt win.
I think Curry outboxes Mayweather, and if this is the Curry of the McCrory fight, he coldcocks him in about three rounds, maybe less.
Floyds workrate is too low, and at mid-range Curry can land some sharp shots and keep him smart. Floyd wouldn't even get in the ring with Curry anyway. As it stands, at 147 Curry has the advantages.
Curry could agree to pre and post fight drug tests,a 75-25 purse split Floyd's way and a 10 minute before the fight weigh in and Mayweather would still find a way not to make the fight happen. If by some miracle Floyd did step it up against Curry (highly unlikely given he kiboshed potential fights with Pacman,Margarito,Mosely etc) then as you said Curry has the speed,ability and combinations to outland the one-shot-at-a-time Mayweather for a unanimous decision.Floyd for all his faults (and they are legion) is one of the best defensive technicians you'll see so a Curry KO is doubtful.
If Mayweather keeps it technical and very safe, avoiding any kind of shoot out, he has enough to win the closest of decisions. Curry was a brilliant front runner at his best, but if you could keep it close early on, you had a chance.
Curry had the jab, speed, and length to force Mayweather to come off the back foot if he wanted to win. I think Mayweather would have to take chances he hasn't shown he's willing to take at 147. Curry by 3 or 4 rounds in a technical showcase.
Not really a close fight, Donald sets the tone early, and after five rounds, scores a knockout of the overmatched Floyd.