OK - tonight is the first time I have had to work on the boat since SUNDAY.
Last SUNDAY I tied the boat to a local dock and tried to get the idle right.
I couldn't get a stable idle.
I could hear a popping noise from the odd bank and when it did the AFR would jump.
Turns out cylinder #5 was the culprit. When I was installing the plugs I thought I heard a snap but after pulling the plug I couldn't find anything wrong and put it back in.
Tonight I pulled the plug and hung it on the front of the engine so I could see the spark. NO SPARK, installed a new plug, SAME results, ohm'd out the wires. OK, installed the plug on #1's wire, good spark. Put #1 wire on terminal #5 ( distributor cap ) NO SPARK
What could cause the system to not fire #5 ???

It is not a firing order problem since it doesn't fire at all

What Dist are you running? An EST type like the stock GM unit or MSD 8366?

The new HOLLEY Dual sinc - has the crank and cam sensor built in. I am running sequential injection. Holley HP EFI, Holley TB. Edelbrock EFI intake and fuel rails, Holley flow matched 66 PPH injectors. The engine runs and idles just not smooth. Cylinder #5 isn't firing most of the time. It does fire about every 10 seconds.

I sent you a PM

maybe a faulty dist cap.try ohming the pins&terminals.

I was thinking that maybe the Hall effect "window" maybe didn't get knocked out. I will look at those things tomorrow.

OK it is not the cap or rotor. I wired a spark plug to the coil and on cranking the engine you can see a miss. Something is telling it not to fire #5. There isn't anything special about the Hall effect sensor - just a window opening triggers it right. The reluctor looks the same for all the cylinders. Is there anything in the programing that could cause this???

See if it fires in batch mode. Are you sure your #5 injector is firing? I had a similar problem with my Accel DFI and turned out to be an injector driver in the ECU. I know yours is different, just reaching.

It is not a fuel problem - it is a spark problem. The system is NOT sending a spark signal to the coil for cylinder #5. I wired a spark plug directly to the coil and cranked the engine with the fuse for the injectors pulled.
Their is a miss in the spark coming from the coil. Why only #5? Is there anything in the programing that could cause it to not fire #5.