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Mercruiser 3.0 carburetor loud suction noise / whistle

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kapo

New member
Hi everyone, I have a loud suction noise coming from my carby that has been getting louder over the past months. I have located the source of the noise and it is coming from a tiny brass coloured hole in the top of the carburetor (see attached picture). If i put the tip of my finger on this hole, it muffles the loud high-pitched vacuum sound, but stalls the engine. Does anyone know what this hole is? (Seems odd having something so vital and yet so prone to blockage on the top like that too?).

carby.jpg
 
It's a pretty consistant noise, but I will check the temperature when I run it tomorrow. However, I was running the engine for quite a while today trying to find the source of the noise and believe it probaby got to that temp - cant be sure though.
 
Spray some carb cleaner into the hole for several seconds...may be full of fuel varnish which narrows the opening and makes it a whistle.
 
Spraying carb cleaner down there was my first instinct, but I am not familiar with this carb so thought I should find out what this hole was actually for first :) ..I presume it's the main air bleed? I am being over cautious perhaps. I suppose a better question would be - is there anything on this carb that could be adversely affected by a flushing of carb-cleaner, or should I just spray away?
 
Update - I have had a better look at this today and sprayed a good dose of carb cleaner.

'boat_tech' is on the right path as the sound does indeed disappear once the engine gets hot - at which point the engine idle also drops and eventually stalls - but that's probably just an adjustment I need to make. Also, the main whistle/suction noise is from the larger hole next to the one I previously indicated :/

Must be the TKS system that replaces the choke on this model? I dont know why it would be getting louder though.
 
Yes, I did - thanks. This is obviously the issue, but I am still not sure why it would get louder over time. I gather there is no solution, just put up with it until the engine warms up :/
 
kapo said:
Yes, I did - thanks. This is obviously the issue, but I am still not sure why it would get louder over time. I gather there is no solution, just put up with it until the engine warms up :/
Click to expand...

I have same issue and cant find the answer here. The link will not open
 
There is a definite "whistle" on TKS carbs while warming up. Mine is initially "loud" but as the engine warms up and the enrichment piston closes off the enrichment jet, it starts to get quiet and eventualy is silent.

Stalling... TKS carbs when using ethanol laced gas seem to like to plug up the jets in the venturi block...It is usually a hard clay colored deposit that is immune to any liquid carb cleaner I've ever tried and can only be removed by mechanical means ( very thin wire)... or supposedly in an ultrasonic cleaner.
 
sandkicker said:
There is a definite "whistle" on TKS carbs while warming up. Mine is initially "loud" but as the engine warms up and the enrichment piston closes off the enrichment jet, it starts to get quiet and eventualy is silent.

Stalling... TKS carbs when using ethanol laced gas seem to like to plug up the jets in the venturi block...It is usually a hard clay colored deposit that is immune to any liquid carb cleaner I've ever tried and can only be removed by mechanical means ( very thin wire)... or supposedly in an ultrasonic cleaner.
Click to expand...

Mine doesnt get any less load stays same even at top throttle. I think it may be in IAC
 
That's because carbed engines don't have IACs

The way the "choke" works in a TKS carb....
There isn't one...
There is an "enrichment circuit" that allows a flow of rich fuel/ air into the carb. As the engine warms up a switch is closed ( @ about 130 F) that energizes a heater in that cylinder (enrichment module) on the side of your carb. It heats up and extends the piston which shuts off the enrichment circuit... As it does this ( over a min or so after engine warms ) the"whistle" changes and eventually goes silent and the idle drops.

If this doesn't happen...
1) enrichment module ( Item #1 in link below) piston passage* in carb is dirty and piston won't move
2) no electrical connection to that module
3) defective temp switch or bad connection to that module
4) defective module.

* i.e. that passage in the carb body that the piston slides in.


http://www.marineengine.com/parts/mercruiser-sterndrive-parts/30l-gm-181-il4/1a020544-up/carburetor


 
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