In article ,
C J Campbell wrote:
The tach should almost always run slower than the Hobbs. The Hobbs is a
clock, but the tach is connected directly to the engine and should only
click off one tach hour when the engine has turned 60 x max rpm.

But it's not "max rpm". In my Comanche (260hp IO-540, redline 2700RPM)
it's 1:1 at 2300RPM. I think the "definition" of tach time is 1:1 at
cruise.

--
Ben Jackson

http://www.ben.com/