2016 4.3 mercruiser efi won’t start

[Jrbastone]

I have a 2016 sea ray with a mercruiser sterndrive 4.3 multiport injection efi engine. The engine was replaced due to low oil pressure. Just the block assembly. All accessories are original to the engine. Went to start the engine and there is no fuel pump cycle and after cranking realized no spark. Hooked up my techmate scan tool and it won’t communicate with ecm. Maybe I’m doing it wrong ? Not a seasoned professional here. I am with 100
Percent certainty sure there is no wires unhooked battery is perfect everything is as it should be. It feels like the ecm or pcm whatever, is not responding or not powering up at all. Any suggestions where to start?

 

[Fun Times]

Is the lanyard safety switch at the shifter up or on?
It seems you’re missing 12 volt power wale up mode.

Do the gauges at the helm power up?

Make sure you have good connections at all the power plugs.

See if you have 12 volt at the engine… Say off the back of the alternator orange wire if there.
50 amp circuit breaker is good?

 

[Jrbastone]

So I’ve got power to the guages, tether kill switch is on and tested working. I’ve checked the 50amp reset relay, tested good. Alternator shows 12+V starter cranks just fine and those little fused positive blocks on the starter tested good. Tested the relays all show 12v on at least 2 pins per relay. Not sure what ones I should be testing tho

 

[achris]

Do you have the engine schematics?
Check the 3 fuses in the holders which is next to the ECU and relays. They are all 20A.
If they are all ok, then use the schematic to find where the power goes and start tracking it. See where it disappears.

Chris......

 

[Fun Times]

Try following this post to see if your engine model has a hard to locate 15 amp fuse back by the 14 pin wire harness connector at the engine, https://forums.iboats.com/threads/hidden-fuse-on-4-3-tahoe-q4-please-help.536975/page-4#post-3863038

So at the purple wire starting from the ignition key switch, through the safety switch on back to the 14 pin all need confirmed 12 volt power to cycle up the PCM if the PCM is working properly internally.
Wiggle the safety lanyard switch on and off a few times just to be sure. Just wondering, do the gauges power on and off when you play with the lanyard?

 

[Jrbastone]

Try following this post to see if your engine model has a hard to locate 15 amp fuse back by the 14 pin wire harness connector at the engine, https://forums.iboats.com/threads/hidden-fuse-on-4-3-tahoe-q4-please-help.536975/page-4#post-3863038

So at the purple wire starting from the ignition key switch, through the safety switch on back to the 14 pin all need confirmed 12 volt power to cycle up the PCM if the PCM is working properly internally.
Wiggle the safety lanyard switch on and off a few times just to be sure. Just wondering, do the gauges power on and off when you play with the lanyard?

I will check if the guages cycle on and off with the lanyard tomorrow, not sure on that one. I’ll also double check how many pins my connector has. It’s the new style thread on connector. But I only saw around 9 pins in it. I’ll confirm tomorrow