We sometimes have customers calling asking why their engines don't start.  After a return of the ECU, we find that it has either not been wired correctly or reverse polarity has destroyed a diode.  If your wire loom has 2 separate wires for the ECU, step one is to combine them as shown here:  

We do NOT believe in a fuse or breaker between the ECU and it's power source, however, we do recommend a temorary in-line fuse of 5A until all initial installation / run-ups have been completed.  Be SURE to clearly mark this to be removed since the fuse WILL fail at takeoff power.