2006 Mercury 115 No start

[Olddeadeye]

I have a 2006 Mercury 115 4 stroke, ran great last year. First time out this season started ok, but it seemed to run a bit rough at times. Yesterday (second time) it started fine, but after a short while it began to cut out and lost power until it finally just quit. Fuel pressure was a tad low so I pulled the fuel module. Module was full of fuel, and perfectly clean inside
I replaced the high pressure pump , but that did nothing. I have also substituted an external fuel source, thinking it could be the fuel. Boat will start on occasion, for a few seconds, but also backfire sometimes. Pulled the fuel rail, injectors spray, fire to the coils, I'm lost.

 

[Olddeadeye]

Injectors spray fine, i corrected and it still came back.

 

[stikboyy]

When was the last time your spark plugs were changed?
there are 3 things a motor needs to run. Spark, compression, fuel. You have confirmed fuel. Compression should be 180psi + with all cylinders being within 10%. Sparks should be able to jump a 7/16" gap with a white/blue spark.

 

[mtsaz]

double, triple, quaduruple check those coils. My optimax coils tested good, had good spark but are breaking down under load and that was causing intermittent stalling, rough idle and it ran perfect WOT---so its a very tricky thing. I borrowed a coil my friend had---and boom- it ran better immediately. I still dont understand it- but make sure that each cylinder drops off when unplugged- I just went thru this exact same thing- but I did a lot more to try and fix my motor---only to eventually get back to spark and fuel- and it was the spark. (coils)