Re: Year lookup
http://www.sterndrive.info/mercury-outboard-parts/18xd_20_25_hp_outboard_parts.html No year but finding the parts of your engine is a great place to start 3.0L, 200 DFI, 225 / 250 EFI parts / drawing
3.9, 4, 4.5, 6, 7.5, 9.8 hp. drawing
6-8-9.9-10-15 hp. parts / drawing
4 Stroke Verado inline 6 lower unit parts layout
18XD, 20 and 25 hp. drawing
30 hp. 2 cylinder 40-50 hp. 2 & 3 cylinder parts
30 hp. to 125 hp. components
35 to 70 hp. 2 / 3 / 4 cylinder components
50 / 55 / 60 hp. components & 40, 50 and 60 hp EFI 4 cylinder lower units
65 hp. thru 225 hp. lower unit parts