The last 140HP IL6 was made in 1978-1979, I believe. It was the same as the Merc 1500, but since Merc introduced a 150HPV6 motor in 1978, they changed the IL6 to 140HP.
There were some earlier 140HP IL6 models, say around 1972.
As was said, the motor is likely worth very little, say $300.