140 HP OMC Caburetor idle adjustment

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leea4

Cadet
Joined
Sep 25, 2012
Messages
13
I have a 1978 140 HP OMC stringer boat. The carburetor is a two barrel rochester 2GC, model 7040083. Does anyone know the correct idle adjustment procedure for this carb? The boat seems to fire fine, but won't continue to run without giving it some gas. I had the carb apart and readjusted the float, and this seemed to help the problem somewhat, but i believe the idle is still off, as it won't fire and continue to run well until it is very warm. The idle adjustment needle valves are set around 3/4 and 1 turn, which according to the break down book was way lower than the starting point which makes me wonder.
 
Grub54891

Grub54891

Vice Admiral
Joined
Jun 17, 2012
Messages
5,915
Re: 140 HP OMC Caburetor idle adjustment

Ya took it apart,did you rebuild it? Sounds like ya didn't. It has to be clean inside,all components taken out,cleaned,wired out,air blown dry.
Just adjusting the float makes thing's worse as now it's not in spec.
Had a similar issue from a customer,running great after the rebuild,here's what I found in there.
image.jpgimage.jpg
 
C

chrisrooter

Seaman Apprentice
Joined
Aug 11, 2012
Messages
41
Re: 140 HP OMC Caburetor idle adjustment

I rebuilt mine over the winter, 2G also, one idle air did not alter engine at all and the other did, rough under power. Also No squirt out of the 2 tiny holes at the top of the carb when you hit the throttle. (Forgot what they are called at the moment) long story short wired through the holes cleaned with spray, rebuild kit new float, ran good out on the water for few, then loaded up and checked 2 tiny holes, again no spray of fuel. So I gave up, ordered me a rebuilt from Florida! $228 plus core charge, 1 yr. warranty. Not playing no more....
 
Howard Sterndrive

Howard Sterndrive

Rear Admiral
Joined
Nov 5, 2008
Messages
4,603
Re: 140 HP OMC Caburetor idle adjustment

one easy way to set idle mixture screw is tighten in until engine starts to die (Lean), back it out until engine starts to die (Rich). Split the difference.
 
B

bezerk1

Seaman Apprentice
Joined
Jul 4, 2012
Messages
40
Re: 140 HP OMC Caburetor idle adjustment

That carb in the picture is not a 2G.
 
L

leea4

Cadet
Joined
Sep 25, 2012
Messages
13
Re: 140 HP OMC Caburetor idle adjustment

Thanks howard! that's the one i was looking for, yes everything in the carb was looking fine, I had the rebuild kit, just didn't need it.
 
bruceb58

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,478
Re: 140 HP OMC Caburetor idle adjustment

grub1rub2 was just showing a carb as an example of what can be inside it. No mention that this was the same as the OP's model engine.
 
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