68 Johnson 9.5 How to adjust carb?

[WarrenW]

I have a Johnson 9.5 model MQ-14E. I believe this is a 68? Anyways, I just put new plugs in it - old ones were in bad shape! I checked the fuel filter - looks good. When it runs, it does great at higher RPMs but it will not idle down. Just cuts off. Then i have to pump the bulb and even choke it at times to crank it. The fuel line is good also. I have adjusted the rich/lean knob on the front to where it runs best.

Now, is there any other adjustment on the carb I can do? I'm sure it could use a rebuild but trying to see if I can smooth it out anymore for using it this weekend. I read where people mention pulling the bowl off and cleaning that part out - where is that on the carb? I cannot see where that is on this motor. I need to buy a service manual for this motor.

Anything I can clean, check, adjust for now on it?

Thanks!

Warren

 

[ezeke]

Re: 68 Johnson 9.5 How to adjust carb?

Take the cover off the fuel pump and make sure that the screen is clean.

Drain the float bowl at the bottom of the carburetor by removing the screw at the front [transom] end.

Look up at the top of the carburetor and you will see the choke bowl - move the choke lever if you don't know where it is.

Just below the choke bowl and left about 3/8" is a small hole. If you blow some carburetor cleaner in there with the little tube that came with it, it will clean out the high speed jet at the bottom of the float bowl. Then put the drain plug back in the float bowl.

1968 is correct:
http://web.archive.org/web/20011223005547/www.evinrude.com/docktalk/modref/jomodyr/JHP9.html

 

[WarrenW]

Re: 68 Johnson 9.5 How to adjust carb?

Thanks for the reply. I know this may sound stupid but I could not tell exactly which screw for draining. Can you see if the screw is shown in any of these pics I just posted online? Or anyone?

 

[perkdp]

Re: 68 Johnson 9.5 How to adjust carb?

#A should be the drain.

Sounds like a combination of a dirty carb / lean idle mixture.
And your getting air in the fuel line and loosing prime.

I expect it runs at fast idle until the float bowl is drained.
But won't idle due to the jet being clogged.

Check the fuel line connection points for dry rot, hardening and clamp tightness.
Shoot the carb cleaner in there like mentioned before.

That's probably all it will take to get it purring.... unless you have the lean idle mixture way off now.

 

[ezeke]

Re: 68 Johnson 9.5 How to adjust carb?

"A" is correct.

 

[Joe Reeves]

Re: 68 Johnson 9.5 How to adjust carb?

(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)

Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.

Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.

Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

Note: As a final double check setting of the slow speed valve(s), if the engine has more than one carburetor, do not attempt to gradually adjust all of the valves/carburetors at the same time. Do one at a time until you hit the above response (die out or spit back), then go on to the next valve/carburetor. It may be necessary to back out "all" of the slow speed adjustable needle valves 1/8 turn before doing this final adjustment due to the fact that one of the valves might be initially set ever so slightly lean.

When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.

 

[WarrenW]

Re: 68 Johnson 9.5 How to adjust carb?

Thanks Joe but where is the needle valve found to adjust on the carb?

Tomorrow I will drain the bowl and try cleaning it some. Today after inspecting again, all of the fuel lines are in great shape. But the one going from the pump to the carb is not very tight. I can move it around easily. It seems the clamp is not tight and some air could be leaking in some. Thanks perkdp on the tip to look at the fuel lines again.

But if someone can just tell me where the needle valve is to adjust, I may be able to get it running smooth.

Thanks everyone!

Warren

 

[ezeke]

Re: 68 Johnson 9.5 How to adjust carb?

The needle valve is connected to the lean rich knob on the front of engine compartment.

BTW, be careful taking that drain plug out. If you drop it it will go to the bottom of the housing and it is a pain to get it back out.

 

[WarrenW]

Re: 68 Johnson 9.5 How to adjust carb?

So the knob on the front is the needle valve adjustment?

Thanks

And for the tip on dropping the drain screw!

 

[WarrenW]

Re: 68 Johnson 9.5 How to adjust carb?

I think I got it running good now! I drained the bowl and sprayed carb cleaner up in there. Then opened the throttle and sprayed down in there. I also adjusted the rich/lean to make it a little richer - the knob was over 3/4 towards lean. Now it idled down and stayed running better than ever!

Thanks for your help everyone!

Warren

 

[perkdp]

Re: 68 Johnson 9.5 How to adjust carb?

That's good news.
That motor should also have an idle stop adjustment on the side
of the side of the motor end of the tiller handle. This doens't change
the idle mixture. It is just a stop so you can set the idle a bit faster or slower
depending on how you're using it.