1996 Johnson 15 hp carb adjustment

[mek07c]

I just got done rebuilding my carburetor on a 1996 Johnson 15 hp model number J15REDG and need to adjust the carburetor idle passage screw and slow speed setting. It cranks just doesn't idle at low rpm and when I open it wide open it sputters and dies. I forgot how many turns for each screw when I disassembled it. I tried reading the top secret file on adjusting carbs and still don't know what to do. Any suggestions?

 

[tashasdaddy]

Re: 1996 Johnson 15 hp carb adjustment

idle mixture start at 1 1/2 out. adjustment 4 turns out.

 

[mek07c]

Re: 1996 Johnson 15 hp carb adjustment

any suggestions for the slow speed setting?

 

[psteurer]

Re: 1996 Johnson 15 hp carb adjustment

The only setting you can adjust on that carburetor is the idle mixture valve. I think you are calling it the slow speed setting. You screw it in until it lightly touches and then back it out 1.5 turns. Then you adjust it in to make the carb leaner and out for a richer mixture. The other two are called intermediate and high speed jets. These are fixed and have no adjustment.

 

[mek07c]

Re: 1996 Johnson 15 hp carb adjustment

There is a screw that is on top of the carburetor that is hidden by the airbox called the screw plug for idle passage (No. 17 on carb. diagram). Is this just screwed in all the way until tight?

 

[bktheking]

Re: 1996 Johnson 15 hp carb adjustment

No , you could ruin the tip, turn it till it bottoms out (by hand) then back it out a turn and a half. Then you can adjust it once running to get the proper mixture, it's all done by sound of the motor running.

 

[mek07c]

Re: 1996 Johnson 15 hp carb adjustment

The screw that I am talking about isn't the needle valve. This screw has no tip just a flat end.

 

[bktheking]

Re: 1996 Johnson 15 hp carb adjustment

That's just an idle passage plug, non adjustable, yes screw in till tight. # 15 is for idle adjustment, sorry for my confusion.

 

[mek07c]

Re: 1996 Johnson 15 hp carb adjustment

Thanks for the help, I got it running good now in the yard. Next, off to the lake, to see how it runs. Thanks again for everybody's help.

 

[mek07c]

Re: 1996 Johnson 15 hp carb adjustment

Just got back from running the motor at the lake. It was running great at the house but differently on the water. It runs exceptional when wide open throttle but is hard cranking. Everytime I crank the motor it has to be choked, and once choke is off will start on the second or third pull. Is it normal to have to choke everytime to start even if the engine was just cut off? I still don't think I have the needle valve set correctly. Currently it is set at 3-4 turns out. When I sat it at 1.5 turns out the motor wouldn't even crank. Also, when I first put the motor in reverse when unloading the boat it dies at low idle. Any suggestions at what I am doing wrong?

 

[bktheking]

Re: 1996 Johnson 15 hp carb adjustment

It will act different in the lake, more backpressure. I suggest you try adjusting the idle in water vs muffs/barrel. You shouldn't have to choke it every time you need to start it, once warm choke usually isn't needed. Sounds like it need some fine tuning.