Question About Low Speed Mixture Screw

[dhami013]

Recently bought a 1980s Evinrude Fisherman 5hp engine. And I noticed the Low Speed Mixture screw in front of the carb. What exactly does that do?

[Way2slow]

It adjust your idle mixture. If the motor is lean spitting and cutting off at idle, you increase richen it up a little, if it loading up and shutting cutting off you lean it up.

Normally, you will have to increase the mixture when you first start it to get it to idle, then after it warms up or you've run it some distance, you will have to lean if back a little to get a good smooth idle. If you do a lot of low speed trolling or moving around, You will appreciate it.

One little note, there are some packing washers under the nut around the stem, if the stem is loose and turns very easy, you need to tighten the nut just a little or it will suck air by them and makes it very difficult to adjust and maintain smooth idle. The knob is also held on by a tappered screw so if you take the center screw out, the knob can be repositioned for better adjustment. Snugg the screw down pretty good to keep the knob from slipping on the shaft.

I just realized you said it was an 80's so it probably does not have the knob, but does the same thing as what I mentioned. Just adjust it so it gives you a good smooth idle when warm. It's better to leave it just a tick on the rich side so it's less likely to lean spit on the cool mornings.

[dhami013]

What does rich or lean mean? It has the numbers 1, 3, 5, and 7. Rich I'm guessing is 7 and lean is 1? I know it sounds like a stupid question but this is really my first outboard. It does have the knob.

[Way2slow]

If I remember right, clockwise should be lean, CC should be rich. Depends on the version carb. They used to put a L and R at each end of the scale.

Lean spit it when, at low speed/idle, the motor makes a cough like sound and try to cut of or cut off. When too rich the motor will be running without the giving the cough but running rough