Re: I have no idea what year my motor is.
Yours is a tough one because 1990 is the year the switched from the Force model and serial number system, to the Mercury system.
You more than likely have a 1990, but might have a 1991.
Many major parts were changed 1990, 1991, 1992.
You will need to check parts listings for ignition components, fuel pumps, carb kits, tilt and trim units, tower shaft,
http://www.crowleymarine.com/parts.cfm