Don't use the integral tach circuit, it's proprietary and it sucks.
Get a modern generic outboard tach and come off one leg of the stator like
they do on all of them today. Faria has several that will work well - I use
one.

Take the "tach line" off the switchbox and re-rout it to one leg of the
stator - then use that as the "signal" line for the new tach.

-W

"Mike" wrote in message
...
I have a 1973 Mercury outboard with Thunderbolt ignition. Anyone kno where
I
can get a tach for this engine?

Mike