Merc 2 stroke 40hp pouring fuel out of venturi at idle...........

[sutor623]

Hey guys,

Got a Merc 2 stroke. Its around 1996 I believe. Its the 4 cylinder motor, like the classic 50. SN: OG058726

Motor was running really rough and barely staying running. I have verified proper timing, spark and compression. Reed petals look good. I tore the carbs down, cleaned them up, put in new floats(set height to spec) needles and gaskets. Got it all back together. Motor wont idle at all, barely runs with throttle. (Primer ball gets good and tight.)

I noticed that even at lower rpms fuel is POURING out of the venturi's. So the motor is getting way too much fuel at idle. I set the idle screws to 1 1/4 turns out per factory manual, then even tried backing out another full turn in increments to no change.

I did NOT pull the welch plugs, but I did let the carbs soak and blew compressed air through them. If I could find the welch plug on its own I would have gotten it. All I can find is it comes in the rebuild kit and one is nearly $100. ( I really doubt there is anything lodged in behind the plugs anyways.)

Any suggestions? Kinda lost here, about to get a used set of carbs and try them out.

 

[schematic]

do both of the carbs have the removable venturis intact? I believe they were black plastic and could fall out on some models

 

[tommarvin]

This is a loaded question lots going on here.
First at low rpm fuel is pouring out the venturis, floats stop fuel from coming out to fast or at all learned this the hard way on a holly double pumper.
second the idle screw set at factory manual is perfect no more no less.
We had a Force 125hp there was alot of garbage under both our welch plugs.A welch plug is a smooth metal cover over the idle air and gas intake. We had to drill a small hole to stick something in it to remove it.

 

[sutor623]

Thanks guys got her purring like a kitten.

Turned out that the little breather holes in the venturi tube were stopped up. I unscrewed them out (with my fingers crossed), cleaned them up and PRESTO!!