Arduino runs at (clock i/o) is 16 MHz (16,000,000). To set OCR1A, I think
you can simply assign to it as a variable:
OCR1A = 0x8000
You might also try ICR1A instead, as I think OCR1A is used to determine
the duty cycle (but the ATmega8 datasheet is very confusing, so I could
be wrong).