The F90TLRD has a stator assembly. It is comprised of a number of components. One of which is the lighting coil. A lighting coil can be a single phase or a three phase device. Does not matter. It still creates AC voltage that is supplied to a rectifier/regulator. In the case of the three phase lighting coil, each phase is measured separately for proper output voltage. At varying RPM's.
Parts diagrams are available all over the innerweb. One of which is yamahaboutboards.com Service manual is available from any Yamaha dealer.