[fesoliveira]

>... a motorcycle could be either gender as it's strongly analogous to a horse, but a car is always female.

In Brazilian Portuguese, we use masculine pronouns for cars ("o carro"). Same goes for boat ("o barco") and plane ("o avião"). This can also be seen in Spanish ("el coche", "el barco", "el avión").

I believe that the gender these things are referred to in languages with gendered nouns is more linked to the etymology and development of linguistics than psychology, although it is very likely that the later has some influence as well.