idle mixture screw replacement - tamper proof cap

[newboatguy18]

Background: Mercruiser 3.0, just did a carb rebuild. Engine shutting off after idling for just a couple of minutes. Works just fine when cruising.

I'm working on adjusting my air/fuel ratio, and I need to get to my idle mixture screw (I did get a replacement in the rebuild kit). However, this thing is really giving me issues. As you can see, I attempted to drill through, thinking I could get a screw in there and just pull it off. That hasn't worked for me yet. A guy got it off in this video after working on it for awhile:

https://www.youtube.com/watch?v=fm9pxRFPth4

However, in most videos on the carb rebuild, the carbs don't have these caps.

Any ideas?

 

[alldodge]

While trying to get it out it looks like you have driven it back in further, so now its against the screw. Suggest a drimmil and real small grinding tip.

Which carb?

 

[newboatguy18]

While trying to get it out it looks like you have driven it back in further, so now its against the screw. Suggest a drimmil and real small grinding tip.

Which carb?

I didn't -- This is where it's always sat. Regardless, I can pull on it all day long, and it won't move. The carb is very similar to the one in the video. Are you asking for the model number?

 

[alldodge]

Is it a Merc, 2bbl, TKS, Q-jet, etc, etc ....

Edit didn't watch the vid, but did just now for 3 seconds, its a Merc 2bbl

 

[alldodge]

The pic for me was the issue, while its clear, its to close to get a perspective of the size. The casing around it in "most cases" can be pried away. Try to split it down the side without applying to pressure to the adjusting screw under the cover.

 

[Bt Doctur]

use a dremil with a small bit to remove the cap, and throw it in the garbage

 

[Bondo]

Background: Mercruiser 3.0, just did a carb rebuild.

Ayuh,..... Welcome Aboard,...... Who rebuilt the carb,..??

How was that done, 'n that screw not removed,..??
Then was the time to trash that cap,......

 

[newboatguy18]

Update -- just got it off. Thank you everyone. Since I don't have a dremel tool, I just decided to drill a few more holes in it. I pried all around the edges, drilled another hole next to the other one I had already drilled. Used needle-nosed pliers to grab it and pulled it off.

As far as why it was still on there -- I watched a couple of videos of carb rebuilds, and both of them didn't touch the idle mixture screw. I have a new one, but if the old one's working, I'm hesitant to pull it off just to put the new one on.

I adjusted the idle speed down to 900, and then played around with the mixture screw to put it right in the middle of too much air and too much fuel. One interesting thing is -- we had the engine idling around 900 on muffs, but for some reason when I took the boat out today, it was idling at 1500. When I dropped it in gear, it was around 800. Is there anything that would make it move that much on its own?

Feel free to give thoughts on all of this.

 

[alldodge]

The mixer screw is removed so the passage it sits in can also be cleaned.

The carb doesn't have a return spring like a car, the throttle cable is what brings the throttle plate closed. Remove the throttle cable off the carb and post or bracket. Adjust for correct idle, then adjust the cable so it just slides back into place. Once there, remove cable again and turn the barrel nut on the cable one more turn so the cable applys a slight prossure holding the carb closed

 

[newboatguy18]

The carb doesn't have a return spring like a car, the throttle cable is what brings the throttle plate closed. Remove the throttle cable off the carb and post or bracket. Adjust for correct idle, then adjust the cable so it just slides back into place. Once there, remove cable again and turn the barrel nut on the cable one more turn so the cable applys a slight prossure holding the carb closed

So are you saying that after I'm at cruising speed, the engine isn't returning all the way to idle?

 

[alldodge]

So are you saying that after I'm at cruising speed, the engine isn't returning all the way to idle?

Yes, most likely
The cable needs to be readjusted every so many years do to wear.

To prove it when the motor is idling high, grab the carb and move it closer to close. If it idles down, then that's your issue

 

[newboatguy18]

Ok, thanks for the help. I'll be trying it out this weekend.