yamaha powerhead serial # i.d.

[droptheline]

I have a 3 cylinder 3 carb yamaha powerhead, it has electronic ignition, and the powerhead has 10 bolts, it was suppose to be a 70hp but its to big. I finally found the serial # after searching forever, was behind the starter i believe what i could see is serial # 487457. anyone know what i got here?
Thanks!