choke? carb? mercruiser 4.3 idle

[j1mmy420]

Hello to all.
I have a 1997 Bayliner Capri with a 4.3 l mercruier lx
My problem is It will not Idle. I just replaced the Gas, Feul Pump, Water Seprator, and Starter I also ran some Seafoam in the Gas to clean things up a bit. Its been about 2 years since the last car rebuild. Here are the syntoms;
above idle (2500 - wot) runs great. But anything less the idle jumps up and doen until it dies. I only have 1 adjustment screw on the front of the Carb. It is turned all the way in with 1 and half turns out.
I tinkered around with the card and If I hold the Butterfly to almost closed it will idle pretty darn good. It will also rev really nice and then drop back to around 1000 rpms witout stalling. Could this just need a choke adjustment??
or is my engine starving for gas?? I appreciate any help you can give me.
I cannot put the boat in neutral without stalling and I have to slam it into gear if i want to keep the motor running..

 

[Haut Medoc]

Re: choke? carb? mercruiser 4.3 idle

Welcome to iboats......
What kind of carb?....
It sounds like you have some crap in there....​

 

[dasnively]

Re: choke? carb? mercruiser 4.3 idle

What kind of carb does it have? If you have to choke it to maintain it running, it sounds like it is starving for gas.

 

[Don S]

Re: choke? carb? mercruiser 4.3 idle

I have to slam it into gear if i want to keep the motor running..

Time for a carb rebuild. BEFORE you destroy your drive!!!!!!
When was the last full tuneup?

 

[Silvertip]

Re: choke? carb? mercruiser 4.3 idle

If you hold the choke closed and it runs better, you have a fuel issue. The choke should be wide open on a warm engine. Rebuild the carb. you should also find two idle mixture screws, not just one on the base of the carb.

 

[Coors]

Re: choke? carb? mercruiser 4.3 idle

slow speed circuit gummed up?

 

[Fishermark]

Re: choke? carb? mercruiser 4.3 idle

If you hold the choke closed and it runs better, you have a fuel issue. The choke should be wide open on a warm engine. Rebuild the carb. you should also find two idle mixture screws, not just one on the base of the carb.

Actually I believe it depends on what carb he has. The mercarb only has one mixture screw, while the rochester has two.

But yes, I agree that it sounds like the carb needs cleaned out at least, and probably completely rebuilt.

 

[j1mmy420]

Re: choke? carb? mercruiser 4.3 idle

I believe I have the mercarb. It only has one adjustment screw on the base.
Also I recently did a complete tuneup, plugs, wires, oil water separator, distcap and rotor. However the carb has been untouched for about 2 seasons. I do not know where to begin. Should I pull the carb and take it apart and clean?? or go ahead and buy the rebuild kit? I am trying to do everything myself. I am ok on cars so hopefully I can do this myself. Any help would be great. Like I said even if the engine is fully warm I have to hold the butterfly about 3/4 closed to get a good idle. If anyone has any pics or schematics that would be helpful

thanks in advance.

 

[Fishermark]

Re: choke? carb? mercruiser 4.3 idle

I had a similar problem with my boat a couple of years ago. I had installed a brand new Mercruiser drop-in crate engine, but ended up running it on some bad gas. I replaced the gas (alomost a hundred gallons!! ), along with the water separator and the engine ran well, but would occasionally die at idle. I took the carb apart and noted quite a bit of water and "gunk" in the fuel bowl. I cleaned out the bowl and never had any problems after that.

You can at least try that and see if it helps.

It's not too difficult to rebuild the carb - IF you have the proper tools and chemicals. (Air compressor - gallon of carb soaking solvent, etc)

 

[Bigdaveaz]

Re: choke? carb? mercruiser 4.3 idle

If you must hold choke partially closed to keep it running, you have diagnosed the problem, buy a kit, disassemble carb and boil it,you have a plugged carb. Dave

 

[Bondo]

Re: choke? carb? mercruiser 4.3 idle

If you must hold choke partially closed to keep it running, you have diagnosed the problem, buy a kit, disassemble carb and boil it,you have a plugged carb. Dave

Ayuh,....... Exactly.........

 

[j1mmy420]

Re: choke? carb? mercruiser 4.3 idle

I just want to thank everyone for the quick replies. I am going to take the carb apart this weekend and attempt a rebuild. I will respond with the results when the job is complete. maybe I can include some pics of the breakdown.
thanks again
j1mmy420

 

[j1mmy420]

Re: choke? carb? mercruiser 4.3 idle`update

Re: choke? carb? mercruiser 4.3 idle`update

Well...
I pulled the carb and did a rebuild. Actually was easier than I thought is would be. I bought a carb rebuild kit that came with all the gaskets etc. bought the paintcan of carbclean with basket also bought 2 cans of berrymans carb cleaner. printed out the specs and step by step instuction pdf file i found on another site.
After I put everything back together the bost fired right up with a nice and steady idle until.............
once the boat warmed up the engine stalled and continued to do the same thing as before. would only idle if i hold the choke partually closed.
any advise
was a sad day

 

[Bondo]

Re: choke? carb? mercruiser 4.3 idle`update

Re: choke? carb? mercruiser 4.3 idle`update

once the boat warmed up the engine stalled and continued to do the same thing as before. would only idle if i hold the choke partually closed.

Ayuh,......

Either,.... You did something Wrong,.....
You missed a Blocked passageway,...
You miss adjusted it,....
Or,....
Your carb is Junk,+ not rebuildable....

'cause you still have a plugged Idle circuit......

 

[Maverick27]

Re: choke? carb? mercruiser 4.3 idle

I don't mean to thread jack...but I have a very similar problem. I fould plugs and get black smoke out of the back when I troll for a while at slow speeds. It then will not stay running and I also have to slam it into gear to get it going without dying to put it back on the trailer. I was told possibly the choke was stuck closed and to get it open to see if that is the problem. Any ideas?

Sorry for the thread jack, just thought there was no need for a new thread on such a similar problem.

 

[Don S]

Re: choke? carb? mercruiser 4.3 idle

Welcome aboard, but Start a new thread. Otherwise you question will be lost at the end of someone elses question. Include your engine specifics.