99, 5.0L Mercruiser, Carbed- misfiring and backfiring

[johno270583]

I assume the graph shows Crankshaft degrees (degrees advance).

Is there any way to test the ICM, or am I doomed to buy another one and hope for the best?

I am pretty sure there is no knock sensor on my motor. There is just the ICM. If there is a knock sensor, Im buggered if I can find it, it is definitely not near the ICM as it is supposed to be, and nothing else attaching to the block, apart from Oil Pressure sensor.