1981 7.5 evinrude

schuder

Seaman Apprentice
Joined
Jun 16, 2012
Messages
38
Can someone please explain to me the use of the slow idle rich/ lean knob on the front of the motor. I got the motor started today in a barrel it runs good and pees really good too :)
 

Vic.S

Rear Admiral
Joined
May 4, 2004
Messages
4,690
I allows easy limited adjustment of the slow running mixture. It should have been set up so that the knob is in the middle of its range when the mixture is correct

If necessary to reset the mixture pull the knob off and set the mixture screw following Joe Reeves instructions on the Engine FAQ board or via the "Top Secret File" in the stickies on this board, then refit the knob.

But if its running right don't mess with it. Just leave the knob in the middle of its range.

(I use the knob sometimes when starting, but this is just my way.
I find if set to its minimum I don't have to be so quick getting the choke off when starting from cold.
and if set to maximum I don't need the choke if starting when slightly warm )
 
Last edited:

tpenfield

Moderator
Staff member
Joined
Jul 18, 2011
Messages
17,621
I have an 1980 Johnson with the same idle mixture knob. It is hardly of any use. My only thought was that the carburetor cannot handle the full throttle range well and so they give you a knob to adjust the idle mixture. . . . but who's gonna sit there and fiddle with the thing while operating the motor :noidea:
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,047
It was put there to allow an operator with some knowledge to fine tune the motor.--------Folks used to know and understand that the mixture screw adjust for variation in local atmospheric conditions.----Fuel quality.-----The knob can not make a full turn because there is no need for that once in the correct range.is established.----It was put there for a reason !-----It allows an owner to get full enjoyment from these wonderful motors.
 

Crosbyman

Rear Admiral
Joined
Nov 5, 2006
Messages
4,914
if it is hardly of any use ……. meaning it has no effect…... then something is wrong with the carb or needle .

Somebody invented those idle adjustments years before your 1980 was born


but if works don't fix it :)
 

oldboat1

Fleet Admiral
Joined
Apr 3, 2002
Messages
9,598
If the motor idles smoothly and goes into gear without stalling, the air mix is probably fine. Adjustments, btw, are in small increments -- 1/8 turn at a time.
 

schuder

Seaman Apprentice
Joined
Jun 16, 2012
Messages
38
Thank you guys for the information It's killing me not being able to get out on the water to play. Water is still frozen
 
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