No Spark

[sr79]

My 1999 Mercruiser 305 engine with Thunder Bolt ignition has no spark. Engine always started and ran well, that is, until the last time I started it. Engine started and ran very rough until it finally stopped, tach was swinging between 1000 and 3000 RPM. With ignition key on purple wire has no power at +side of coil, should it be hot? Purple wire also goes to the ignition amplifier. I need help! Thank you, Dennis

 

[alldodge]

Without power to the coil, check for power at the choke with key ON. Could be something as simple as the key switch went bad. With the tach bouncing, this could be power of the tach is shorting out.

Run though the TBV trouble shooting guide and see what show up

 

[tank1949]

My 1999 Mercruiser 305 engine with Thunder Bolt ignition has no spark. Engine always started and ran well, that is, until the last time I started it. Engine started and ran very rough until it finally stopped, tach was swinging between 1000 and 3000 RPM. With ignition key on purple wire has no power at +side of coil, should it be hot? Purple wire also goes to the ignition amplifier. I need help! Thank you, Dennis

Salt water boat? Check for corrosion. The green stuff!

 

[Scott06]

Also check man overboard switch should be red toggle switch on throttle control. This cuts off power to ignition circuit