Setting high speed jet on Johnson 4 horse

[sutor623]

Hey fellas, as some of you know I have been working on a 2 cyl. 1969 Johnson 4hp. Cleaned out all of the water passages, and changed all engine gaskets, she fires right up and runs superb. Anyway, what I am dealing with is I am trying to figure out a good spot to set the high speed needle. I started with the needle out 1.5 turns and it seems to run a little rich and slow at WOT. As I turn the needle to lean, the rpms pick up (obviously). The question is, since I do not have a tach, where is a good place to run the motor safely and efficiently? I could literally lean the motor out and the rpms would continue to climb. I just want a good basepoint to set the needle at. Thanks!

 

[kbait]

Re: Setting high speed jet on Johnson 4 horse

I get close by adjusting it at a relatively high idle in the barrel.. usually it's about 3/4 turn out from gently seated. On the first boat run, wind it up full throttle and turn the knob in (clockwise) until it slows. Open (ccw) until it slows again. You'll find a range where it runs fastest. Be on the rich end of that range (just before it starts to slow) and leave it, you're good to go. I then fine tune the low speed (at slow idle). Same deal, except the final setting is a little richer than the 'best' rpm. Let it slow just a bit and leave it. It'll idle wicked slow all day if your ignition is good. Good luck. Also, top secret files at the beginning of this forum is full of excellent info.

 

[raczekp1]

Re: Setting high speed jet on Johnson 4 horse

in outboards its not as dangerous to set up high speed needle comparing witch chain saw where rpm gets to 13000 rpm

 

[HighTrim]

Re: Setting high speed jet on Johnson 4 horse

Im with Kbait, I leave them a tad on the rich side.

I start at 3/4 out, 1.5 is quite rich for the high speed. It typically ends up being between 1/2 and 3/4 out from gently seated, but varies.

 

[samo_ott]

Re: Setting high speed jet on Johnson 4 horse

There's a high speed needle on a '69 4hp? I thought they went to fixed jets in the mid 60's. Did they keep two adjustable jets on the smaller engines then?

 

[HighTrim]

Re: Setting high speed jet on Johnson 4 horse

There's a high speed needle on a '69 4hp? I thought they went to fixed jets in the mid 60's. Did they keep two adjustable jets on the smaller engines then?

Little guys still adjustable, Im not sure at what year they changed without looking into parts manuals.

 

[kfa4303]

Re: Setting high speed jet on Johnson 4 horse

This may help.

http://forums.iboats.com/showthread.php?t=167352

 

[sutor623]

Re: Setting high speed jet on Johnson 4 horse

Thanks guys!! I am used to the 'ol 1.5 turns out and start from there, but I guess this lil guy is different. Also, all of my other motors have a fixed high speed jet, so this is a little intimidating. What a huge difference it is between 1/4 turn. And Kbait, she trolls ssssoooo sssslloooooowwwwwwww it is INSANE! I bought her with this fresh ignition system. Guy said the motor had a clogged cooling system (did it ever!) so I bought her for $100 and cleaned all the passage ways and put in all new gaskets. I have $150 in her and boy am I glad!