Motor will not start/run

97 150hp v6 carburetor.
Motor was blown when I bought it.
I rebuilt this motor myself using manual.
4 pistons and cylinders were fine.
1 cylinder was bored out next size and I used a new piston for this.
1 cylinder destroyed and sleeved to std size I used a good used piston to replace.
New rings.
New gaskets.
Carbs and fuel pump cleaned and verified.
Carbs do not have mixture screws.
New fuel lines.
Removed auto oiling components.
I left all of those small rubber hoses.
Removed idle stabilizer component.
Now using 50:1 in tank.
New voltage regulators aftermrkt.
New switch boxes aftermrkt.
Cleaned up old wiring.
New battery cables.
Good battery.
New impeller.
Primer bulb pumps till firm and I hear fuel going into carbs. No leaks.
Motor cranks fine and starts for 1 second and stops.
Repeat
Repeat
Have not spent much time on it but now I want to get going and see what's my next move.
Where do you think I should start to get it running?

What is the compression? does spark Jump a 7/16" gap on all cylinders? Why all the new electronics?

I'll check all that.
Voltage regulators looked burned up.
Switch boxes wiring was green with corrosion all
thru.
Previous owner said idle stablizer component
failed which caused the detonation.

110 psi all cylinders.
History
I remember when fitting the rings to the cylinders the gap
was .025 on all of them which seemed incorrect since the
manual showed much less (I don't remember what) so I
called the manufacturer and they said .025 was acceptable
and I installed them.
The cylinders were machined correctly.
Anyway, I'll check the spark gap tonight.

Made time to check the spark gap and it was all over the
place. I think I need to re visit the corrosive wire(s) issue.
One minute I had a 7/16 spark and then nothing.