There is a way to tell if your tach is off. Move the plane so a street
light is shining on it from behind you. Run it up. A two blade prop
should appear to stop at 1800 rpm, a three blade at 1200 and 2400.
This is due to the strobe effect (the light blinks on and off).

"Jon Woellhaf" wrote in message news:riRcd.414274$Fg5.254744@attbi_s53...
Mike Noel wrote that he had his analog tach overhauled and that it is, "...
now giving accurate readings across the RPM range."

Mike,

How do you know it's accurate?

Just curious.

Jon