Expert advice needed on 200EFI Merc

Looking for Chris at Dockside Marine- the Merc Master's advice please:
2001 Merc EFI has a rebuilt block done by some place in the East. New ECM, Injectors are cleaned and calibrated, new coils, replaced mechanical fuel pump, serviced VST, all and all done by certified Merc. It only starts and stay running with advanced cold start throttle. Cam roller and all lined up well, but does not stay running at idle position. Smoked like hell and I had converted its system to 50:1 premixed. Still smokes like a white clound. Spark plugs are all wet, but no water bubbles. Could it have a bad reed? Or could it have a crack head? Compression 124psi on all 6, spark present thru timing light. I am not certified and don't want to redo a certified's rebuild job. But I've done thousands of successful rebuilds for this motor. Please once again point me to the correct direction as of where to start to save this baby Merc. After I converted to premixed, I had it idle for 10min and blast down the river for 15min, but again it shuts off at low idle and can only start up with advanced cold start throttle! If I waited a while then the rpm automatically increased itself, only then I can quickly move to neutral, slam into gears and come in. Kept floating down the stream quite far!
Thanks a bunch and happy holiday.

Did you get this engine from the guys in Pennsylvania?

First I would get the factory manual and go through the complete link and synch procedure, This includes checking the TPS voltage. I would check and make sure the fuel pressure is correct.
I know you said the VST was clean but, there is a small filter inside the regulator and they get packed up with debris. This will send the fuel pressure out of spec.

Second, If the problem is still present I would Check the recirculation system and the check valves. There are different mappings for this system for FI and carbed engines, Incorrect mapping will cause your engine to run slobberingly rich with fuel, especially Having to push the throttle forward to start and the wet plug condition.


Third...Run the serial numbers and make sure you have the correct computers on your engine.

Thank you very much Chris. I don't know where the owner got the motor from. All the Marine Shops out here pointed him to the wrong direction and he went changing all kind of parts. Fron your advice, it seems like the other mechanics went too far off track. He won't be able to afford to have it redone all over.
The fuel pressure reads 35-38psi at running.
And yes, it is a flooding issue. I can't save this baby. He will have to get his warrantee on the rebuild. Thank you very much Sir. Have a Merry Christmas and a Happy New Year.

Checking and repairing the re-circ system does not cost anything. You just have to get the correct diagram.

Chris ...I dont remember EFI motors having a recir systrm like carb motors unless its a odd ball 2.5.

Chances are it is a 2.5. If the rebuild shop took a carb block and rebuilt it and did not change the recirc system to the EFI....you know what will happen, fuel will pool.

Your correct and there are 2 places to avoid on the east coast from other websites Iam on.

Not an expert, but maybe?
First how about a serial#
The fuel pressure could be off by 2 # and affect the system(I know it happened to me)