I got my Mp41000 sierra ignition switch today and on the back it has m,b,m,c,i and s. On my Merc. switch it has a,b,c,d,e and f. Correct me if I'm wrong, but I'm thinking the e and f off the old switch will go to the m's on the new one. "A" wire will go to the b post . The b wire on the old will go to the i post on the new. The choke wires aren't important to me because the electric choke linkage that goes from the choke solenoid is missing and I can't find another one, so I just use the manual choke lever. It's a Merc 350 35 h.p. 1969 by the way.