78 Evinrude, 9.9hp, requires choke to run at full throttle - what's the problem?

[mlisabell]

The engine idles nicely but when I apply full throttle the engine speeds up but soon wants to stall. If the choke is pulled up it will than continue to run but does smoke. If I adjust the richness for full throttle the unit won't idle. I've since rebuilt the fuel pump and cleaned the carburetor but no improvement. Any suggestions? Thanks in advance.

 

[Daviet]

Re: 78 Evinrude, 9.9hp, requires choke to run at full throttle - what's the problem?

When you cleaned the carb, did you remove the high speed orifice and made sure that it was not plugged or restricted?

 

[Rick.]

Re: 78 Evinrude, 9.9hp, requires choke to run at full throttle - what's the problem?

That is a symptom of a dirty carb. If you're sure the carb. is clean (as per suggested above) then you might try pumping your primer bulb at WOT to see if that improves performance. Let us know how it's running. Best of luck. Rick.

 

[mlisabell]

Re: 78 Evinrude, 9.9hp, requires choke to run at full throttle - what's the problem?

Carb was cleaned in a sonic bath cleaner, going to remove carb and inspect and clean orifices.

 

[gozierdt]

Re: 78 Evinrude, 9.9hp, requires choke to run at full throttle - what's the problem?

If you buy the whole carb kit, you will get replacement metal plugs that will allow
you to remove the plugs in the carb now, and be sure to get the idle and high
speed orifices open by pushing a wire through them. Also makes sure there isn't
any crud in the passages leading up to the orifice.

Here's "LeeRoy's Ramblings" article on carbs:

http://www.leeroysramblings.com/Johnson_9.9_carb-fuel_pump.htm

Lots of good information...

 

[mark1961]

Re: 78 Evinrude, 9.9hp, requires choke to run at full throttle - what's the problem?

Carb was cleaned in a sonic bath cleaner, going to remove carb and inspect and clean orifices.

Have a close look at the orifice that protrudes through the float.....did you replace the needle and seat and adjust the float level to spec first time round?