Adjust mixture knob for cold weather??

Captain Caveman

Captain Caveman

Ensign
Joined
Mar 1, 2005
Messages
924
I've got a 1979 Evinrude 35hp motor. As we're getting into the cold season here, with temps in the 20-40 degree range, should I be messing with the knob to richen the mixture?

Is there a sign to watch for that would indicate that the mixture needs to be more rich, or should I adjust just based on ambient temperatures?
 
jbjennings

jbjennings

Captain
Joined
Jul 18, 2007
Messages
3,903
Re: Adjust mixture knob for cold weather??

I'm no expert although I regularly run mine at 20 to 40 degrees when I'm duck hunting. If it's not lean sneezing at idle I wouldn't worry about adjusting it. I usually leave the choke out a little longer is all I have to do at that temp. I'm not ever lucky enought to get temps. below 20 degrees F, so I have no idea below those temps. Are you fishing that cold or duck hunting?:) I find that lots of folks would be better off not messing with those mixture knobs at all unless they know what they're doing.;)
JBJ
 
Captain Caveman

Captain Caveman

Ensign
Joined
Mar 1, 2005
Messages
924
Re: Adjust mixture knob for cold weather??

I'm usually going to and from my cabin, just before the lake freezes...but I'm also heading out to go fishing.

I agree. I don't like to mess with the mixture because it seems to run fine, although my motor always has a sneeze to it. Maybe it's been running to lean all along?
 
Joe Reeves

Joe Reeves

Supreme Mariner
Joined
Feb 24, 2002
Messages
13,262
Re: Adjust mixture knob for cold weather??

Sneezing...... turn the slow speed adjustable needle valve counter clockwise in 1/8" turn segments until the sneeze ceases.
 
jay_merrill

jay_merrill

Vice Admiral
Joined
Dec 5, 2007
Messages
5,653
Re: Adjust mixture knob for cold weather??

Cold air is more dense than hot air. Because of this, yes, there is some logic in feeding a little more fuel into the mixture. In a small engine, however, the amount of the appropriate change is probably negligible.

If you are in doubt, adjust your slow speed needle valve in accordance with the service manual's directions, and then adjust the high speed needle valve. In most motors, you will find the "sweet spot" once idle has been set, by running the motor at WOT and then leaning the mixture until the rpm falls off. You then enrich it slowly until you return to maximum rpm.
 
F

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,195
Re: Adjust mixture knob for cold weather??

I live in Florida and on my 35 I have to set my low speed needle a bit richer in the winter, so I am quite sure you guys in freezing weather have to, also.
If it is sneezing when it is warmed up, it is too lean. Just give it a tweak toward rich till it stops doing that. No fear, it isn't rocket science and you won't hurt anything, and you can always put it back to where it was.
 
Captain Caveman

Captain Caveman

Ensign
Joined
Mar 1, 2005
Messages
924
Re: Adjust mixture knob for cold weather??

Usually it just sneezes when the engine is first started, then idles decent the rest of the time. I'll probably just leave it alone.

I was mostly worried about blowing something up if I ran at WOT these next couple weekends.
 
You must log in or register to reply here.
Top