93 mercruiser 4.3 choke

[mark89coupe]

I have a 1993 Stingray with Mercruiser 4.3 Alpha One Gen 2.

The boat starts fairly well when cold but when the engine it hot it takes about ten seconds of cranking to start. I did notice the choke is in the same position hot or cold.

I was planning on a carb rebuild kit soon but was wondering if there may be a problem with the choke. The choke linkage goes down into the intake manifold. Should I change those parts also?

 

[Don S]

Re: 93 mercruiser 4.3 choke

I did notice the choke is in the same position hot or cold.

Is that same position open or closed.
The choke should be closed when you start a cold engine, and open as the engine warms. Does the choke open as the engine warms up?
When you shut the engine off, the electric choke coil will close the choke again, but it takes it a little bit.

 

[Kainon]

Re: 93 mercruiser 4.3 choke

sorry this is a little lengthy.

the choke rod shouldn't go down into the engine, it attaches to the back of the electric choke coil, an older type will attach to a "Choke Stove" Coil that sits on the Intake Manifold. ( I prefer the older version )

the coil could not work if its not getting 12v when the engine is running or KEY is on. ( good reason to not leave key on when not using the engine )

The coils can also stop working, 3 screws and 3 small tabs on the screws are all that needs to be removed to remove the coil. coils can be reversed if the tab is pointing in the wrong direction and need to be set in the proper position to close the choke properly and open at the correct amount when the engine is warming up.

If the choke is set to tight, the engine will run rough or flood out, too loose and it will require multiple throttle pumps to start or keep running.

There is small cylinder that the lever of the choke and coil attach to, behind the plate behind the coil, this can sometimes bind up. removing and cleaning with a brillo pad, or fine steel wool does the trick.

The choke needs to be "SET" when you first start the engine, unlike fuel injected engines you need to "pump" the throttle to at least 1/2 way the first start, sometimes all the way and if the carb is set right, only ONCE else you can flood the engine causing it to not start or blow black smoke (unburned fuel)

If the choke is opened when the engine is warm, and you have to re-start, you shouldn't need to "pump" the throttle, especially if the engine was just shut off. If you do it can mean the "idle Mixture" setting isn't right or the carb needs to be cleaned/rebuilt.

the only part that usually needs to be replaced is the choke coil.

 

[mark89coupe]

Re: 93 mercruiser 4.3 choke

Its definately a coil type choke. I didn't notice any electrical hook up. There is a vacumm type thing on the side of the carb. the linkage of the vacumm thing meets up with the linkage of the choke.

Yes, the choke stays open all the time. It will be very hard to start after the engine is warm.

What kind of carb does it have? Its a 4brl carb, two mixture screws on front base of the carb. Does not look like a rochester quadrajet.

 

[Kainon]

Re: 93 mercruiser 4.3 choke

Lack of at least 1 wire to the Carb says someone forgot something. Sometimes there's a Ground wire that goes to one of the 3 screws.

When you first start in the AM ( cold engine ) the choke needs to be closed.

THe Vacuum thing on the side is a "CHoke Pull Off" so that once the engine starts it "Slightly" Opens the choke plate.

the 4bbl carb you have is a "webber" Style.

 

[mark89coupe]

Re: 93 mercruiser 4.3 choke

Is there a pict or diagram of the carb the way it should look?
I will take a look at it later and shoot a pict of the choke side.

The choke pull off, what makes that work?

Are the webber style carbs similar to rebuild as the quadrajet?

 

[Kainon]

Re: 93 mercruiser 4.3 choke

Vacuum from the carb when the engine is running pulls on the diaphram in the choke pull off, pulling a lever that opens the choke.

Webbers are not similar to the Quadrajet, they are like the Edelbrock Carbs.

 

[mark89coupe]

Re: 93 mercruiser 4.3 choke

I looked and did not see any wires that would be for the carb.
I took a pict of the carb cold. Choke looks like it is adjusted correctly.

Next two pics shows how the diaphram is linked to the choke. Does this seem right?

 

[Kainon]

Re: 93 mercruiser 4.3 choke

yea, you look fine, you have what I call the "choke Stove" type, no wires, just the coil heats up from the Exhaust Gas Crossover in the intake manifold, heats up the coil and opens the choke. If its 90 out.. that could be the right position, should be closed more when its colder, say 50-60F.

Then the choke pull off opens it to about there when the engine starts.. if it doesn't then the pull off needs to be changed, you can take the pull off, off.. suck on the hose/port a little should pull the choke arm IN, then when you release the arm should go back OUT.

 

[Kainon]

Re: 93 mercruiser 4.3 choke

with the pull off pulled in you bend the arm so the choke opens to the correct amount ( if needed ).

THe 2 screws at the front of the carb adjust the air/fuel IDLE Mixture, and if not correct will cause starting and idleing issues.

 

[mark89coupe]

Re: 93 mercruiser 4.3 choke

Ok then, it must be the idle mixture.
Is there a link on how to properly adjust the idle mixture? I will try this before I do a rebuild.

 

[mark89coupe]

Re: 93 mercruiser 4.3 choke

Did a search, found the webber manual. Any tricks to it or directions are good enough?

 

[mark89coupe]

Re: 93 mercruiser 4.3 choke

I adjusted the idle mixture screws. Starts right up when engine is warm.

 

[Kainon]

Re: 93 mercruiser 4.3 choke

Sorry, couldn't respond sooner.. Good job on the Idle Mixture !!!

I like to fine tune the mixture in the water with the engine warm, in forward and tied to a trailer or dock. (sometimes you can tweak it just a hair better) I also prefer a 600rpm in gear idle.

 

[mark89coupe]

Re: 93 mercruiser 4.3 choke

Worked out great, Thanks.