Still wont run

"1969 mercruiser 120 will star

"1969 mercruiser 120 will start for a second and then die. went through the fuel lines, has new fuel pump, rebuilt carb from shop, new intake gasket, new points set to spec, plugs, cap rotor, resistors, good even compression. strange enough it will run with identical car carb. so figured it had to be carb and took back to shop and they couldnt find anything wrong. it will also run if you hold the choke almost shut( giving it just a little air,but when i let go it opens up and dies i can also keep it running if i pour a little gas in it.) what the hell!!!!! i have been doing this with the air cleaner off....the air cleaner wouldnt have any thing to do with it right? also the fuel pump has a line that looks like an upside down "u" going to the inlet and outlet...can i take that off and run it?"

"[b]"it will also run if y

""it will also run if you hold the choke almost shut( giving it just a little air,but when i let go it opens up and dies i can also keep it running if i pour a little gas in it.) what the hell!!!!!"

Ayuh,...

The Idle Circuit in the carb is Plugged....

Clean it out, or replace the carb...

"also the fuel pump has a line that looks like an upside down "u" going to the inlet and outlet..."

No Idea what you're talking about,...

Got a Picture,..??"

"no picture but the inlet to t

"no picture but the inlet to the fuel pump has 2 hose fittings and so does the outlet, and a short line goes to each of the 1 remaining outlets from the inlet to the outlet, some sort of bypass....... if the idle circuit is plugged then i guess the guy who did my carb sucks huh? i took the top of the carb off to look at the float it seemed o.k. is the idle circuit by the fuel inlet which works the choke?"

"The idle circuit on most carb

"The idle circuit on most carbs appears as a very small hole in front of and also below the throttle plate (not the choke). Cleaning them can be difficult at times. Plugged idle circuits do not always respond to the "dunkit and reinstall it" or to "carb cleaner in the fuel" methods of carb overhaul. Often they need to be taken apart totally and the idle passage either blown clear or in really bad cases, reamed out with a VERY FINE soft copper wire strand.

When you get it fixed, install a REALLY good MARINE fuel filter on the engine between the fuel pump and the tank. In this era of ethanol laced gas, I'd consider one with a water seperator, preferrably a drainable one."

i would think another possibil

i would think another possibility would be an air leak/ major vacuum leak due to the fact that when he closed the choke it responds well.
i had an old holly carb that wore the buttery shafts where it went thru the baseplate. had similar issues.
have you tried spraying carb cleaner around the carb while you keep it running with the choke?