Not to be a negative Nelly, but
Chevy, same as any other competitor, GM and Chevy has nothing to do with it. Cars, motors, drive train is nothing like anything in the real world. Would like it again if they went back to stock car
Thanks
This is your motor
https://www.mercruiserparts.com/350-mag-mpi-alpha-bravo-1a611928-thru
Having Alpha drive then your fuel pump is under the port side motor mount
This is the fuel rail, and item 18 where to measure
https://www.mercruiserparts.com/bam/subassembly/31753/15044/90
Could use a serial number of motor to verify what your configuration is?
Measure the fuel pressure at the rail, should be 43 psi at 1800 rpm. Should be close or slightly higher up to WOT
The Purple wire going to the ALT should have 12V when key is turned ON and 0V when OFF
Your ALT needs 3 connections to work correctly
Orange wire - Output wire to Battery via the Starter post
Black wire - Ground
Purple wire - Excite wire that turns the ALT ON when key is turned ON
If you have...
Many things are possible, but without some testing we're just guessing
Other things
Check plugs, wires, cap
Check for spark
Fuel
Kind of like need to start somewhere
Serial number shows 5.7 Carb not throttle body, and thanks for SN
What type of pops?, backfires?
If water got into the motor a valve might have been bent.
Agree use BT's copper fittings and it won't happen again
Fella at my dock replaced the thing twice before he started just leaving the drain out of it during winter. Appears the system never fully drains and if plug is reinstalled more water leaks into it later and cracks it
Might have a vacuum leak but most times they don't go and come back.
Does the throttle linkage apply any pressure to help close the TB when at idle?
It should apply a slight bit of force to close. Adjustment is normally with engine OFF, remove cable from TB and see if the Throttle is fully...
Your post list where you take readings and how the motor reacts to each change, to me that's part of testing.
The old and new IAC are doing the same so while the new style is better then the old, the old was not the issue from what I read.
What does Diacom show for injector pulse time, does...
Check the throttle cable goes from full open to full close on the Throttle Body
Oil Temp going to zero could be it lost a ground. If other sensors like the rev counter it could be causing all kinds of issues
Most likely going to need to motor scanned
Accurate enough to get an idea on the oil filter. See 300+ is not good, under 300 could be ok. Check after a good run and don't let it idle a long time. After the oil filter is what the bearings see
Run some 10W40 or 15W40
