Just did several upgrades on a 92 350 merc setup, using a edelbrock carb with elec choke, could not find a place to get ign on power except main power to coil, with grounds out the system and will not let it fire, could find no other wires in harness that would work...any idea's ? thanks Rob

I believe the purple right where it connects to the alternator.

http://www.boatfix.com/merc/Techbk/94/94hg4d.pdf

If the alternator has an "ac tap" it works good for the choke. Omc has that style of alternator cant remember if merc does

You can, per say, (S or STA terminal((Stator)) terminal which is AC, but most newer carbs like Edelbrock have chokes that strongly advise to use 12+vdc, This is why Edelbrock says not to hook to the distributor, again meaning the S or STA terminal found on some alternators...like Ford and Merc's mando.

The terminal on the back of the Mando alternator that has the purple wire hooked to it has switched 12vdc of course.

Any purple wire in that harness is connected to the others. Did you hook it to the purple or gray at the coil? If you ground out the purple you'll blow a fuse or pop the main breaker not just kill the ignition.

gray wire, did not blow any fuse, runs fine with wire unhooked..

Gray wire is the ground signal from the ignition module. Hook the choke wire to the positive side. Purple wire.

there is a gray wire to + coil, where I tried, will ck for the purple at the alt, the wiring at the alt has been hacked up by someone...

Doh ! One Gray wire should be tach wire the other gray from ignition module as mentioned, both which is on the - of coil. And of course all purple wires are switched +.

Here some decent pics for wiring of the Mando altternator Merc uses on most engines:

Sounds like your coil is wired backwards. The grey (or greys if more than 1) should go to negative, purple to positive. But I don't like hooking anything to the coil.