1969 Johnson 4hp, help needed

[mysonchristopher210]

I know this is a rookie question but, I have never had a motor this old. I just bought a boat that has a 1969 4hp Johnson on it. It looks almost brand new. It will start and run as long as I keep playing with the manual choke. I noticed two knobs on the front of the motor too the right of the choke lever. The both go into the carb and say " lean and rich" I know it has something to do with my air/fuel mixture. Can anyone tell me what they are for and how to adjust them so that the motor will stay running without messing with the choke.

Thank you

 

[nwcove]

Re: 1969 Johnson 4hp, help needed

read the top secret file at the beginning of this thread, it will help you out alot.

 

[kbait]

Re: 1969 Johnson 4hp, help needed

I consider that one new! Top secret as stated^ http://forums.iboats.com/showthread.php?t=299680

Welcome aboard and good luck!

 

[HighTrim]

Re: 1969 Johnson 4hp, help needed

The top knob is for the slow speed needle. Turning it to the right, clockwise, leans out the air fuel mixture. Turn it to the right, clockwise, until it gently seats. Then back it out 1.5 turns. That is your starting point. While underway at idle on the water, start slowly turning it in, clockwise, small turns at a time, allowing it time to respond. When you find that she wants to die, or mildly backfire, turn it back out, counter clock wise about 1/4 turn. Within that 1/4 turn is the ideal position.

The bottom knob is the high speed needle. It functions the same as the low but is for adjusting the fuel/air mixture at high speed. While underway at WOT, do the same adjustments as stated above to get your best WOT RPM. The only difference here is the starting point is 3/4 of a turn out from gently seated, not 1.5 like the slow speed.

Once the needles are set, tighten down the nuts and I like to leave the slow speed pointing straight down and the high speed straight up so that I know if they have moved.

This all may be best done after cleaning/rebuilding the carb, which is what it may need.