air/fuel mix adjust

[Matthew A.]

Hello everyone,
I replaced the air/fuel mixture screws with brand new ones due to the needle tips being damaged from overzealous seating practices by the previous owner. Starting at 1 1/2 turns out from fully yet lightly seated, the motor begins stumbling and coughing brought on by a lean condition with the mixture screws backed out roughly 1/2 turn each from being fully seated. [adjustments made in 1/8 turn increments] During the rich adjustment the motor begins showing signs of being too rich by a very rough and low idle at about 2 1/2 turns out from being fully seated. The lean adjustment is fairly straight forward as small amounts of adjustment make very distinct changes to how the motor idles. An adjustment of 1 1/4 turns out from being fully seated and the motors idle increases considerably as compared to 1 1/2 turns out from seated. And keeps increasing with each adjustment until the motor stumbles and dies. However, determining exactly were the over-rich condition is, is not as easy to distinguish as a quarter turn in either direction once a rich condition is reached makes very little change in how the motor reacts. With that being said...I set the screws at 1 1/2 turns out. Exactly at the recommended starting point. Should I be looking for a more exact set point or is where I determined the final set point pretty much it?

 

[pnwboat]

Re: air/fuel mix adjust

Sounds like you've pretty much got it set correctly. Final test is to get it in the water under a load. When you put it into forward gear, starting from a stand still, say like when you're trying to get a skier up, the motor should get up and go without hesitation. If it stalls or hesitates, it's probably a little too lean. Make the mixture richer 1/8 turn at a time to get rid of the stalling/hesitation. Make sure the motor is nice and warmed up before you do this. These motors are a little cold natured and don't react well to this test when cold.

 

[Frank Acampora]

Re: air/fuel mix adjust

On a hole shot, if the engine sags and then picks up, it is too lean; adjust out about 1/8 turn at a time until smooth acceleration is acheived.

If it stumbles then clears itself and accelerates, then it is too rich. Adjust needles in 1/8 turn at a time until the engine accelerates with no hesitation.

The two conditions sound completely different--you should be able to tell lean from rich.

But, of course, my standard warning: Never-Never-Never go leaner than 3/4 turn out from lightly seated no matter what the engine says it wants.

 

[Matthew A.]

Re: air/fuel mix adjust

Hi Frank and thank you for replying.

I made all the adjustments after several hours of fishing to be sure the motor was in optimum condition for doing so. Considering the motor doesn't show the slightlest stumble or hesitation during hard acceleration from idle speed, 1 1/2 turns out must be it. Once again thank you for your help and advice. It is as always very much appreciated.