Mariah Carey Brett Ratner on The LOVE BOAT!!! (PHOTO)

EXCLUSIVE

Mariah Carey and Brett Ratner have pulled a Swift/Harris … they are full-throttle together.

This pic was taken Saturday on a yacht in St. Barts. Sources — let’s just say accurate to the boat — say they’re all over each additional. She’s really into him and he is nuts for her.

Ratner recently said he and Mariah were just really good friends, calling rumors of…