trying to put a new switch on a old merc 500 ols switch is labled a,e,b,d,f new switch is labled i,m,s, a m b c here is where i get lost i have 7 markings on my switch and only 6 screws. i believe a is accessory, b is battery, c is choke ,s is start, and i is ignition , now i have been told...