how to tell if a Mercruiser Thunderbolt IV Igntion is bad? I was running in the ocean the other day and the bracket that holds the ignition mod broke off and was laying on top of the engine left the boat overnight and now it wont start , got fuel and it turns over. I tried a different coil no good. can the ignition mod be tested with a volt ohm meter and if so what to look for thanks

http://www.marinemechanic.com/site/page251.html

That is a good chart.
They do not mention checking the black ground connection.

if the bracket broke off the ground probably went with it. try clamping bracket back together with a vicegrip(clean surface first) if it starts just replace the bracket.

The bracket has to be grounded as well as the black wire. Not having the bracket grounded will cause a no start/no spark condition.