Thunderbolt IV Help

I have 1987 twin Mercruiser 340s with Thunderbolt IV ignitions. About 3 weeks ago I was cruising for about an hour when one engine died suddenly. No coughing or bogging beforehand. Plenty of fuel. Wouldn't restart. Got back on other engine. Engine is not getting any spark. The engine has the new sensor that does not have terminals protruding from it. Just 3 wires. The TB IV diagnostic schematic contemplates removing wires from the terminals as part of the test procedure. IOt may be obvious but how do you do the test when there is no wire to disconnect?
To complicate matters, I tried starting the other engine yesterday just to run it and it wouldn't start. Turns over good and has fuel. Put a spark tester on one of the plug wires and am getting intermittent spark, i.e. on the no. 1 cylinder, spark does not coincide with timing mark. The mark goes around seveeral times and only sparks once.

Any thoughts on what's going on here? Thanks.

The three wire style (which is all that is sold now) should have bullet connectors. The sensor pig tail (three wires) is about ~10 inches long if I remeber correctly.....
The black wire has a ring terminal on it and should be attched to ground.

Dont forget to check the interuptor switch to see if it is working properly. If the switch is internally shorted closed it will short the ignition to ground thus no spark. Check this first. Also make sure with the key in the on/run possiton you have 12 volts to + of coil........test light is best for this and it should be nice and bright like it were across the battery