Re: merc no start, spark on left side cylinders no spark on right side of motor any h
If you model has the two ignition modules each firing one bank of cyl's, there is two test to determine if you have either a bad stator or a bad module (switchbox).
First test, disconnect the Bias wire (white) linking the two boxes together, retest for spark. NOTE: Do NOT attempt to start the motor. If you now have spark on all cyl's (both banks) then the Bias circuit in the box that was always working is bad and blocking the other box from firing. It is recommended to replace switchboxes in pairs unless they are already been replaced witih CDI Electronics boxes in which case it is only necessary to replace the box with the bad Bias circuit. Note; a switchbox with a bad Bias CAN be used on a 3 cyl engine (75 to 90 HP).
If still no spark on one bank then proceed to the second test.
Switch the red and blue stator wires between the boxes, then retest for spark. If spark moves to the other bank of cyl's then the stator is bad.
