New Long block will not accelerate

[joefran]

Installed new long block 350 mag mpi/ wo4 serial number. 2005
Motor starts and idels fine. But will not accelerate above 1700 rpms ( under no load just throttle ) anything above it is just all over the place rough . Spme popping and some white smoke,
1 No error codes on vessel view
2 Mobile mechanic put mercruiser computor on all sensors reading fine but he has no idea what is causing the issue.
3 timming checked
4 fuel pressure 40 psi
5 new injectors
6 check plug wire position / could be a bad wire?
7 new distributor cap and rotor

Thinking about sending out ecm for testing.

All Ideas would be appreciated

Thanks
Joefran

 

[Fun Times]

How was the timing checked?.. it’s a special procedure to install the high voltage switch type distributor…. no timing light used on this design.

Just in case, try searching online how to install Mercruiser high voltage switch as it may help.

 

[AllDodge]

In-Gear switch
If motor things it's not in gear it will cause a misfire to protect the motor

 

[Dieter]

Was the old long block running ok. Might do a sanity check compression test to ensure the LB is ok

 

[2004 searay]

i second alldodge, also check the grounds. make sure all the grounds are good, and tight. if the mechanic scanned the system and all indicators came back ok, then its highly doubtful its the ecm.