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Carburetor needle either too rich or too lean

1

1999john25hp

Member
1999 Johnson 25HP

Looking for some help setting up my carburetor correctly.

Symptoms: excess fuel around carb, fuel smell, oil slick behind boat, easy to flood if I squeeze the primer bulb.

I tried taking apart the carburetor and replacing the float and gaskets. Replaced the needle valve (both the needle and the valve screw it seats into).

The o-ring that came with the (cheap) rebuild kit was a little thicker than the one on there already. That slight extra height seemed to help in terms of reducing fuel flow, because the primer bulb felt firmer and I could hear that less fuel was flowing into the bowl when I pumped it. Started right up, but then would bog and stall, even when I gave it throttle. It would only keep running when I pulled out the syringe to the red ring.

Tried adjusting the idle air/fuel mixture screw to no avail. Tried flipping the float, in case I had installed it upside down, but no change. Went back to the old thinner o-ring and things are back to what they were before: engine runs, but fuel everywhere.

Seems like too much fuel is getting in the bowl with the thin o-ring and too much with the thicker o-ring.

What other adjustments should I try? Bending the float?
 
Also inspect the emulsion tube. When you have the bowl off. I had a motor that someone prior to me owning cracked the tube trying to remove it. It was almost impossible to prime without flooding, and had a similar rich/lean issue it was a treat to get dialed in I ended up having to get an eBay carb. Make sure your float is level when flipped upside down and that your float hang is where it needs to be I think around 1 1/8” I’m definitely not an expert but just little things I’ve come across as I have been learning myself. Mostly the hard way haha
 
CreatureKid said:
Also inspect the emulsion tube. When you have the bowl off. I had a motor that someone prior to me owning cracked the tube trying to remove it. It was almost impossible to prime without flooding, and had a similar rich/lean issue it was a treat to get dialed in I ended up having to get an eBay carb. Make sure your float is level when flipped upside down and that your float hang is where it needs to be I think around 1 1/8” I’m definitely not an expert but just little things I’ve come across as I have been learning myself. Mostly the hard way haha
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Thanks! I’ll check that.
 
What was your motor doing / not doing?---About 50 years ago 2 gentlemen came into an authorized Johnson dealer complaining about the carburetor.-----Turns out it was a blown head gasket.-----So what trouble shooting have you done for this apparent " rich " condition.----Checked thermostat ?----Made sure linkages are set up correctly.-----Compression test?----Fuel pump diaphragm replaced ?----Quality oil mixed at 50:1?----The Amazon parts are NOT installed here.
 
racerone said:
What was your motor doing / not doing?---About 50 years ago 2 gentlemen came into an authorized Johnson dealer complaining about the carburetor.-----Turns out it was a blown head gasket.-----So what trouble shooting have you done for this apparent " rich " condition.----Checked thermostat ?----Made sure linkages are set up correctly.-----Compression test?----Fuel pump diaphragm replaced ?----Quality oil mixed at 50:1?----The Amazon parts are NOT installed here.
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Like I said, excess fuel around carb, fuel smell, oil slick behind boat, easy to flood if I squeeze the primer bulb.

Def could be something other than the carb. How do I diagnose a blown head gasket?

Yes, already ordered a quality carb rebuild kit. Lesson learned.
 
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