spud;
Don't know your s/n but if it is a 1971 it comes up as a model 1500101,
Parts listing:
http://www.crowleymarine.com/mercury-outboard/449.cfm
Oddly enough, the original Merc p/n for the tach, which you will see under MISCELLANEOUS PARTS/ACCESSORIES, 79-73370A3 apppears to be still available if you are adamant about sticking with the original:
http://www.marinepowerservice.com/B...Num/1115100/Doc_Part_nbr/63296/pickyear/1985/
Do you know what type of control box you have?
Gerry