1989 mercruiser 5.7 no spark

[ltfella]

My mercruiser 5.7 has n spark. I tested the ignition coil at the pos and neg side and they both say 12.5 volts when I touch the neg to the battery. replaced htat and of course same thing.its a thunderbolt IV ignition.do the negative wires from the merthode need to be hooked up to that or is that just for the trim?

 

[makomark]

you need to follow the test procedure for the TB-IV ignition system, not just make random voltage measurements....

Mercathode is a separate and independent system from the TB-IV...and had NOTHING to do with the trim.