Success

"Y'all might get a kick ou

"Y'all might get a kick out of this:

Merc 25. Wanted to calibrate my built in tach with a portable Tiny Tach. EMF interference screwed up the readings on the Tiny Tach, so I did what I always do: I wrapped the other plug wire with aluminum foil to block the interfering EMF.

Unfortunately--like a jerk--I didn't shut the motor down and do it right, I merely draped the foil over the top plug wire (with the Tiny Tach lead wrapped around the lower wire). Motor started skipping badly then died--no spark! The EMF had jumped from the spark plug wire to the primary wires of the coil and into the spark box. Groan!

So what was blown out? Obviously, the sensitive spark box, right? Wrong. It's fine. The charging coil is what went! Imagine that.

Thanks to my good buddy, who lent me a spare one, the problem is resolved.
Jeff"

"Hehe, cool! So far I've o

"Hehe, cool! So far I've only managed to do this the other way around - frying a Tiny-Tach by getting a spark to jump from the plug lead to the sensor wire.

Interesting, though, that you report the Tiny-Tach causing interference, as I've had the opposite effect. The tach works fine but messes up my fish finders big time (rotary, digital, all the same). Foil wrapping worked to clear up the false echoes but it still causes the Lowrance to mysteriously "reboot" at certain RPM, somewhere just above fast idle.

"As we acquire more knowledge, things do not become more comprehensible, but more mysterious."
-Albert Schweitzer"

The Tiny Tach wasn't the c

The Tiny Tach wasn't the culprit--I was. To avoid interference I drapped that aluminum foil over the other plug wire and zapped the charging coil.

Jeff

"Yeah, I know.. Neither was it

"Yeah, I know.. Neither was it in my case (bad plug insulation + doing the job in the rain). "