Choke issue?

I have a 1992 4.3 mercruiser and I think it is a mercruiser carb. It is also a 2 barrel. my problem is this as soon as I start the engine it will idle for about 10 second and die. After that the choke is fully opened. Well if I hold the choke barely open maybe a 1/4 of the way open it will idle fine, if I move it from that spot either direction it will start to die immediatly. So is my choke messed up or could it be more engine side. When I have it idling there is no miss or no indication of any engine problem.

Re: Choke issue?

The choke could be out of adjustment, or inoperative.
Engine of and cold, move the throttle up just off idle position and look at the choke plate. It should be closed and have some spring tension on it. If not, adjust it so it just closes and a notch or 2 tighter.
Now, turn the ignition key to the run position. The choke coil should heat up and open your choke plate over the next few minutes.

Re: Choke issue?

Ok the choke is working properly but i still can't keep it running. It will idle fine at first and as the choke opens it will start running rough the farther it opens the worse it gets until it dies. Would low compression cause this or does it seem to be more of a carb issue. The carb has been gone through and the fuel filter has been changed.

Re: Choke issue?

It's a carb, not fuel injection. You have to give it some throttle to clean out the over rich condition from the choke, or it dies... until it warms up. Sorry, but carbs are like that, and they take some user input.

Re: Choke issue?

I don't have the option of backing it into water to rev it until it warms up. So what would be the proper way on muffs without messing it up.

Re: Choke issue?

If what Don has you trying doesn't work, your next step will be to check your idle mixture. If you have to hold the choke 1/4 of the way open to get it to idle, that indicates your idle mixture is too lean, or your floats are not adjusted correctly.

Re: Choke issue?

Well that did not work I ran it at 2000 rpms for over a minute holding the choke in a position to make it run. Gradually decreasing throttle. I did get the choke open to about 3/4 but anymore than that and (blah) it dies. I have adjusted the idle mixture screw all over the place and doesn't change a thing. So i'm back at 1-1/4 turn out. So whats the best way to adjust the float it is a 2 barrel mercruiser carb.

Re: Choke issue?

You could have any number of problems causing that. Vacuum leak, water in the fuel, plugged up carb, who knows.
What has been done to this engiine since it ran ok?

Re: Choke issue?

Well it has set for years. So I decided to get it from my parents. When i got the boat the manifolds were cracked and a core plug was out of the block. I have pulled the engine and replaced all the core plugs changed the oil. and replaced the manifold. No visual signs of external cracks. The carb was gummed up very bad. I took it apart and cleaned everything made sure it was very clean. The electric fuel pump wouldn't work at first had to keep trying and tapped on it until it finally broke free. And i have replace the fuel filter. As far as the fuel tank goes it was bone dry. I also replaced the main fill hose that goes to the fuel tank the old one was starting to dry rot. I only have about 1200 dollars left in my budget for the boat this year so i am trying to get it running to see if i need to replace or rebuild the heads or block. That is about everything i have done to it that pertains to it running.
Oh and I did soak the cylinders down for a few days before manually rotated the engine a few revolutions.

Re: Choke issue?

The carb was gummed up very bad. I took it apart and cleaned everything made sure it was very clean.

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Ayuh,... My guess is you missed the idle circuit somewhere,+ a replacement carb will probably Fix that part of it...

Have you tested/ looked into internal block cracking,..??
Is the oil level stable while you've running it,..??

Re: Choke issue?

Have you tested/ looked into internal block cracking,..??
Is the oil level stable while you've running it,..??

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No i have not tested/looked for internal cracking.
The oil seems to be stable and not milky but i have not been able to run long, due to idle issues.

Re: Choke issue?

This morning I woke up and decided to spend some money and get the carburetor prof. rebuilt. 119 dollars well spent the boat starts and idles great.

Now its time to see if the block/ heads are good.

Thank you everyone for your advise/ help, This is a great sight for advise and hopefully when I get this project finished I will be able to give some out myself. Well until next issue, happy boating.