2015 Mercruiser 350 mag- crank but no start

[Eparker]

The 350 Mercruiser is in a Monterey 295sy.
The other day after running beautifully for several hours, it sputtered for 3 seconds and died.
It now cranks fine but won’t start
I figured it had to be a fuse on circuit breaker, but couldn’t find one that was blown.
Fuel pump works, and I changed the fuel filter just in case
Does anyone know of any hard to find breakers or fuses that would directly effect the ignition?
Thanks!

 

[Scott06]

Will it start if you advance the throttle in neutral ? If so maybe issue with iac valve which controls idle airflow.

 

[Eparker]

Will it start if you advance the throttle in neutral ? If so maybe issue with iac valve which controls idle airflow.

Great question. I tried that. It does not change anything.
Since my original post, I have also determined there is no spark at the plug

 

[Fun Times]

All the gauges seem to work normal when you first turn the key on before cranking over engine to start?

Does the RPM gauge seem to move up a bit when cranking engine over?
While the list of possibilities could be long, you may have a failed crankshaft sensor as that is where things start in order to get spark 'all other things working normal to deliver proper operation of the crankshaft sensor itself.
Any warning horns sounding off at all?
Having the engine serial number helps at times too.