Logo

1972 Mercury 20hp not getting fire

R

RBaron

Guest
My 1972 mercury 20hp is not ge

My 1972 mercury 20hp is not getting fire. Kill switch O.K.Am getting voltage to coils from stator. Points making and breaking. Coils not firing????
 
"This has a Thunderbolt II ign

"This has a Thunderbolt II ignition, so there should be a "capacitor" integral to your stator.

The high or low speed windings power is rectified and stored. When the points "close" the capacitor should release it's charge to the coils.

How do you know you have voltage to your coils?

They don't decide whether or not to fire.

Once the charge is released/triggered by the points, the power is passed from the capacitor through the coil to the plug - nothing there to switch or stop it unless it is grounding out before it gets to the coil....

If the coils are getting power, then either, both coils are shot, they are grounded out, both plug wires are bad, or the plugs are both bad.

The odds of "both of anything" simultaneously going is kinda remote..."
 
Wire coming from stator to coi

Wire coming from stator to coils show's voltage when I turn moter over but I don't know any values. I checked the coils with ohm meter and they checked the same. Unlikely that they would both be bad and check the same?? Do you know what I should get out of stator? A/C or D/C Thank you for you'r help!!!!! Ron
 
"Sorry, I don't have a fac

"Sorry, I don't have a factory manual for this far back. But can tell you that the leads going to the coils should be DC.

The stator produces AC but it's rectified to DC and stored in the Capacitor. The points then release it to the Coils.

In the slightly "newer" ignition systems the voltage being fed to the coils is usually in the 200-300 volt range, the coils then upconvert to about 35,000 - 40,000 volts.

Sorry, can't even really say if your ignition should/would be in that range, but would suspect something similar...."
 
"Sorry, I just found a note in

"Sorry, I just found a note in my pile of "yet to be filed" - the capacitor on your system sends approx 1000 volts DC to the coils...."
 
My 25 hp Mariner will not fire

My 25 hp Mariner will not fire on either cylinder. I've replaced the switch box and rectifier but still no fire. It's a stick stear/remote start. Any ideas as what to check for voltage at the stator/trigger/alternator leads?
 
"Charles, do you have a serial

"Charles, do you have a serial number for the motor - it will help with specs..."
 
"Graham,
I believe I've s


"Graham,
I believe I've solved my problem. The trigger coil showed to be opened on my ohm meter. My repair manual says it should have a reading of 750 to 1400 ohm. I pulled the coil out of the housing and sure enough the top several hundred windings were burnt. I've got a new one on order and I should be back to pestering the Crapie and Catfish by next Wensday or so.
proud.gif

P.S. The manual shows DVA of 4V+ on the trigger coil and 180V+ on the charging coil. I'll verify this when I get everthing put back together.
In the mean time, keep up the good work on the board and I'll try to pitch in and help out if'en I can."
 
Back
Top