Tuning carb on '75 Johnson 4 HP?

JNG3

Recruit
Joined
Apr 13, 2016
Messages
4
I have done a search and read some of the FAQS. However I really want to make sure I have this right.

Outboard is a 1975 Johnson 4hp weedless model 4W75A. I need to fine tune the low speed and high speed needles. I have read the "carb needle adjustments" article written by Joe Reeves. If I am to understand the directions correctly, I need to turn the needles in (lean) until engine starts to die then back out 1/4 turn. I just don't want to end up with an engine running too lean.
 

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,226
Do it on a boat, on the lake, and don't be afraid of it. You won't kill it. Run at wide open throttle and turn High speed knob to the right till it starts to lose power, then back to the left till it regains power, but not so far that it starts to blubber (called four-cycling). Slow down to idle and do the same with slow speed knob. With that one, it will probably sneeze and or die if too lean. Too rich and it won't idle well.

Short story is set them where it runs the best. It isn't rocket science.
 
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