Loose bolts on 88 3.0 mercarb

[wtg2320]

I've been having issues with my mercarb. I have to screw my throttle screws nearly all the way in before I can get my rpms where they need to be. I was checking the bolts that hold the top of my carb in and I noticed that I could pull one all the way out. Some of the others would just spin without getting tight. I bought new bolts that were a bit longer, they will now tighten down, and I have noticed that once I have done this it is starting to idle much better. Would tightening this down help with the rpms? What other issues would this help fix. I was shocked how loose the bolts were. Thanks in advance.

 

[harringtondav]

Your tightening was good therapy. Carbs work off the negative manifold pressure to deliver and atomize the fuel. Any 'vacuum' leak will alter the carb's designed function. Vacuum leaks generally cause a lean mixture, more noticeable at idle. Your carb to manifold gasket may be old, and have shrunk or relaxed. This could have caused the loose fasteners.

 

[wtg2320]

Hopefully this will also help my issues of hard starting while hot, or maybe that is a different issue all together. I am taking it out tomorrow so I guess I will see

 

[harringtondav]

I don't know if the Merccarb's adjustment screws control air or fuel in the idle circuit. But if you enriched the mixture compensating for the loose carb, it could cause hot starting. Try setting them back to where you started and see if the idle is OK. Factory settings tend to be 1 1/2 turns back from fully seated. If your idle holds OK, hopefully your hot starting will also improve.

Also one way to help a hot, rich mix or flooded engine start is to slooowly push the throttle wide open, and snap it back to idle once your engine touches off.

 

[wtg2320]

Thanks for the tip

 

[Alumarine]

It sounds like the OP is talking about the machine screws for the air horn.
Are there approximately 8 "bolts"?

 

[wtg2320]

There are approximately 8 screws, yes. I didn't know it was called an air horn.

 

[achris]

... Some of the others would just spin without getting tight.....

This means the threads in the carb body are stripped. The fact that you bought longer screws (they are screws because they don't tighten up against nuts. If they did, they would be called bolts) and they did tighten up is confirmation.

Sorry to be bearer of bad tidings, but with so little thread holding them in, they will also eventually strip. When that happens, you will need to replace the carb.

Chris. ...

 

[wtg2320]

That is what is was planning on doing in a few months