squeal coming from carb

[91EuroF3]

I have a 1991 Malibu euro f3 with a Mercruiser bluewater 5.7 Chevy 350

I just started hearing a squeal that seams to be coming from the carburetor yesterday. I thought it was a belt making the noise but it sounds like its coming from the carburetor. Sometimes it will go away for a second if I rev it up a bit in neutral but comes right back most of the time.

Anyone had this problem or have advice?

 

[Idlespeedonly]

Re: squeal coming from carb

Check for a vacuum leak.

 

[91EuroF3]

Re: squeal coming from carb

thats what I had been thinking from reading other posts. Is it a problem if I keep running it? Or will it just make noise?

 

[Idlespeedonly]

Re: squeal coming from carb

I hav had a couple that would whistle. I my past experience it was coming from the butterflies. If you have a leak it will cause a lean condition. Which is not ideal. Will it hurt anything? Maybe not. Now if it worsens, it may cause problems. Personally i would fix it, if it is a leak.

 

[91EuroF3]

Re: squeal coming from carb

whats the best way to check for the leak? Not sure what the butterflies are, I have an idea but you might as well tell me

 

[04fxdwgi]

Re: squeal coming from carb

whats the best way to check for the leak? Not sure what the butterflies are, I have an idea but you might as well tell me

The butterflies are the round discs you see in throat of the carb when you look down into it. They are attached to the throttle shaft and open to allow more air in to increase engine speed and close to restrict air to reduce engine speed. At idle, the engine is trying to suck a ton of air past the butterflies that are almost completely closing the air passages through the carb, thus making the whistling sound.

With engine running (and plenty of ventilation), squirt some carb cleaner around gasket areas and fittings. If engine speed or "squeek" changes, you found your leak. Chances are, it's just the normal sound of air rushing past the closed butterflies at idle. You can also try draping a towel loosly (for just a few seconds) over the air cleaner and see if the sound muffles. If it does, again, it's probably just the air sound.

Unlike an automotive engine's air cleaner, the spark arrestor is wide open, very low restriction, not enclosed, and not muffled by a paper element and every little sound can be heard through it.

 

[91EuroF3]

Re: squeal coming from carb

Thats what I was thinking the butterflies were. If I remove the spark arrestor the noise sounds like it is coming from inside the carb not from down around the gaskets. I have not had time to spray and check for a leak yet but should have time tomorrow.

 

[91EuroF3]

Re: squeal coming from carb

so I used a propane torch and ran it around the gasket under the carb and the was no change in the idle or noise. The engine idles very nice and is not running rough at all. If it were a vacuum leak shouldn't it idle rough? I went out and ran it around for a while and the noise seams to come and go a bit while its idling.

any ideas?

 

[04fxdwgi]

Re: squeal coming from carb

so I used a propane torch and ran it around the gasket under the carb and the was no change in the idle or noise. The engine idles very nice and is not running rough at all. If it were a vacuum leak shouldn't it idle rough? I went out and ran it around for a while and the noise seams to come and go a bit while its idling.

any ideas?

Your everyday, run of the mill carb noise. Close the hatch, hit the water and have fun. Turn the stereo up if the noise at idle bothers you. (or invite your mother in law along, to drown out the noise). LOL