My boat engines DD 671N/J&T (1984) use mechanical takeoff for the tachometer sender. Questions:
1. The take-off is in the back side of the engine
(see image). I need to know what is "Engine takeoff ratio" (1/2:1, 1:1, 1-1/2:1 or 2:1)? to set my new tachometers.
2. I will like to calibrate my tachometers, using my osciloscope. The sender is a SIGNAFLEX (8 pulse per turn).
With the sender outside the engine
, if I manually turn the needle at 1000 RPM
, the sender will give me 1000x8 = 8000 pulses in one minute, equivalent 8000/60 = 133.3 pulses per second = 133.3Hhz.
With the sender installed in the engines takeoff port, do I have to consider the "engine take-off radio" to calculate the real engine RPM
?. In other words, does the "engine take-off radio" affects the sender reading or just is to setup the tachometer?
Suppose that the engine take-off ratio is 2:1 and I measure 133.3Hhz in my osciloscope, does the final RPM is 1000/2=500RPM, 1000*2=2000RPM or 1000RPM?