Throttle screw

[wtg2320]

Hello all. My question is should my throttle screw be touching the U shaped metal piece? The friction caused by this is not allowing my choke to operate as it should. When the choke plate closes it will not allow the arm to move, which keeps the choke plate open, and it was to be forced to move the arm at all.
How difficult is this to fix, and how can I fix it? I am trying to attach pictures of the issue as well. Thanks in advance. I apologize for not using the proper terms for these parts, I am new and learning as I go

 

[Bondo]

Ayuh,.... There ain't no throttle screw, 'n just what motor, 'n carb are ya workin' on,..??

Generally speakin', dumpin' the throttle to Wot on a cold motor, sets the auto-choke,....

 

[wtg2320]

Sorry, 3.0 mercruiser. I was always told the screw in the pictures was a idle screw. Whatever the name of that screw, it is not allowing freedom of movement due to the pressure on the U shaped piece. I added pictures in my original post to help make up for my ignorance when it comes to the names of these pieces. I called it a throttle screw in my first post, but I meant to call it an idle screw.

 

[alldodge]

The closer of the choke plate is closed by the choke spring on the other side of the carb. The throttle control and idle cam (not really a cam on a boat carb). The two pieces come together at the top of the carb and are free to move independently. The choke is stopped by a tab which is also the reason for the choke to close when the motor is cold, the throttle must be pumped at least once.

With the choke closed, you should be able to open the plate with your finger, and when removed the spring tension from the choke will close it



SO if the choke plate is not moving then remove the choke plate, plate rod and hardware, free it up and put back together

 

[wtg2320]

The problem is that the idle screw is preventing the freedom of movement

 

[alldodge]

The problem is that the idle screw is preventing the freedom of movement

Understand what your saying, but IMO the screw should have no issue with freedom of movement of the choke. Only way it can hinder the movement is if it is not moving freely and is some how bound up. If you open the throttle enough (motor OFF) so the idle screw no longer touches the cam. With this the choke and the cam should move very easy. The only tension would be if the motor is cold and you feel it from the choke spring

 

[wtg2320]

No Title

The screw is hitting the U shaped piece is not allowing the arm to move fully, which is preventing the choke plate to close all the way. It is hitting the piece in the enclosed picture, and will not allow the choke plate to close. I backed the idle screw back a bit, which is now allowing it to move freely, now I will have to see if I have to adjust the idle screw again, I think the idle screw was to far foreword, but I am not sure how the idle screw works yet

 

[achris]

It's correct that the choke doesn't move when the idle speed screw it touching it. The choke is 'set' when the engine is cold by you 'stroking' the throttle. Once the throttle starts to open the screw comes off the choke lever and the bi-metal spring closes the choke. When the engine is warm that same bi-metal spring keeps the choke open.

 

[wtg2320]

So you are saying I shouldn't have backed the idle screw out? I might have to adjust the idle screw then

 

[Bt Doctur]

That screw controls the idle speed, what is wrong is the top tang is bent upwards and it should not be.

 

[achris]

So you are saying I shouldn't have backed the idle screw out? I might have to adjust the idle screw then

That screw is designed to run on the 'cam'. It's to adjust the engine idle speed, and if it's not running against something, it have no purpose in life. Put a calibrated digial tacho on the engine and screw that screw in or out until the engine is running at the specified speed. Then close the engine box and enjoy boating.

When the engine is cold, pump the throttle once and that puts the screw off the cam and allows the bi-metal spring to close the choke. That's how it's designed.

Chris..

 

[nola mike]

OP, I think you might be a bit confused on what's being said here. When the throttle is anything above an idle, that screw doesn't contact the cam, and the choke plate (and cam) should move freely. When the engine is cold, the spring on the choke closes it. When you pump the throttle before you start, you move the idle screw off the cam, and the choke closes. While the ignition is on, a current through the spring opens the choke. Again, as long as you aren't at idle, the choke will open on its own. Note that if you're at idle, that screw WILL prevent the choke plate from moving freely. What the screw does is control the idle speed. If you back the screw out to the point where it isn't touching the cam, your throttle plate will close all the way and you'll get way too low of an idle, and likely stall. So try this:
Engine off/cold: Push throttle all the way. Leave it there. Screw will be off the cam. Choke should be closed at this point. Check to see that the choke plate moves freely. It should.
Now turn the ignition on (but don't start). The choke plate should start to slowly open, and should open fully within a few minutes.

The specs for initial idle setting is to turn the screw until it contacts the cam, and then do 2 more turns in.

 

[wtg2320]

Thanks for all the help, what is a tang and can I bend it back to where it needs to be

 

[wtg2320]

Sounds like it was correct in the first place, I'll have to figure out the rough starts somehow. Thanks again for all of your help!

 

[Bt Doctur]

 

[alldodge]

It might be bent but could also be just an optical illusion. The coke should move freely and when cold as the throttle is moved it should close. Move the throttle and see if the choke moves easy with your finger. If it does move freely but does not close when cold the choke pot needs to be adjusted

 

[wtg2320]

Hate to keep asking silly questions, but what is the choke pot and how is it adjusted?

 

[Bt Doctur]

Ita a bi-metallic spring that expands and contracts to move something. Similiar to the electric element that heats the spring or hot exaust that heats it
If mounted to the intake manifold ,you bend the rods, if electrically operated, loosen 3 screws and turn it to open or close the choke plate

 

[alldodge]

What carb do you have? If you don't know take a pic of the whole thing

If its a Merc carb like the one below, as BT mentioned the 3 screws are loosened to adjust

 

[wtg2320]

Got you, I understand. Thanks again for your time and help