Hi,
Working on my Mercruiser 165 70's. And still doubting the 8-9V towards pos Coil side.
In this forum it was clear that during cranking you put full battery voltage to the coil to start but once running it should be around 8-9V to avoid sparking of the points.
Point are completely new with correct setting of the dwell. Used my scope to do this, is very clear.
But the ballast resistor is still bit unclear, as this was originally missing on my engine.
My coil is around 1.6ohm (should be normal). When engine runs I count on around 13.5V.
So this means that if I want 9V over the coil => 9V/1.6ohm= 5.6amps. This leaves 13.5V-9V=4.5V over the resistor at 5.6amps => 0.8ohm.
So the ballast resitor should be around 0.8-0.9ohm.
When I measure this setup with key to ON and engine not running the reading at pos coil makes sense.
But I initially thought that also during running Engine you should read this 8-9V at coil. But this is way higher. Close to 10-11V.
With Engine running: I put the scope on the Pos coil and the you clearly see that during dwell-period (points closed) you have about the 8-9V. But during points open it clearly shoots up close to the 13V. (I think the kick-back of the coil)
So for me this confirms the High Volt reading on my voltmeter during running operation. As a Voltmeter uses averages.
What is now my question, as I want to install the right value of resistor:
When we talk about the 8-9V in this forum are we talking when engine is NOT running or during running engine. Because with a Volt-meter this will give clearly different readings.
I guess it is when engine is NOT running. Running versus not running gives different V readings with same setup. Or I am clearly still missing something.....
Regards
PS: sorry for the long post
Working on my Mercruiser 165 70's. And still doubting the 8-9V towards pos Coil side.
In this forum it was clear that during cranking you put full battery voltage to the coil to start but once running it should be around 8-9V to avoid sparking of the points.
Point are completely new with correct setting of the dwell. Used my scope to do this, is very clear.
But the ballast resistor is still bit unclear, as this was originally missing on my engine.
My coil is around 1.6ohm (should be normal). When engine runs I count on around 13.5V.
So this means that if I want 9V over the coil => 9V/1.6ohm= 5.6amps. This leaves 13.5V-9V=4.5V over the resistor at 5.6amps => 0.8ohm.
So the ballast resitor should be around 0.8-0.9ohm.
When I measure this setup with key to ON and engine not running the reading at pos coil makes sense.
But I initially thought that also during running Engine you should read this 8-9V at coil. But this is way higher. Close to 10-11V.
With Engine running: I put the scope on the Pos coil and the you clearly see that during dwell-period (points closed) you have about the 8-9V. But during points open it clearly shoots up close to the 13V. (I think the kick-back of the coil)
So for me this confirms the High Volt reading on my voltmeter during running operation. As a Voltmeter uses averages.
What is now my question, as I want to install the right value of resistor:
When we talk about the 8-9V in this forum are we talking when engine is NOT running or during running engine. Because with a Volt-meter this will give clearly different readings.
I guess it is when engine is NOT running. Running versus not running gives different V readings with same setup. Or I am clearly still missing something.....
Regards
PS: sorry for the long post
