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1974 Evinrude 9.9 issue

M

Magensbay2

New member
Hi there, new to the forum here. My father had an old ‘74 evinrude 9.9 laying around in the garage for about 20 years and my son and I decided to get running again. We have spent the last 2 months on and off working on it and even repainted it. Looks brand new once again. We got it running really well on a stand so the other day we took it to our stock pond to test it out. At full throttle, it only seemed to run on one cylinder. But, if I adjusted the low speed adjustment valve to really lean, it would rev up and take off. But, as soon as I came down on the throttle it wouldn’t idle and would die. It would be hard to start back up unless I turned the low speed adjustment more rich. In the beginning, we did a compression test and check for spark, replace the ignition coils and all that. Does this seem like maybe a fuel delivery problem? I’m skeptical of the fuel line hose and the bulb that we have, it seems kind of cheap. My next thought was to possibly go to a little bit larger diameter, fuel line hose and replace the bulb with a better quality one.
Any help with this would be greatly appreciated, my son is itching to take this thing out for an adventure!
 
Did you ever disassemble & clean the carb?

With it idling in the pond in neutral, pull one plug wire & see if it hits one 1 cyl. Reinstall & then do the opposite. Same results?
 
We actually found a new old stock carburetor and replaced the original, but kept it for spare parts. We still ‘cleaned’ up the new carb and checked it out so I don’t think there’s a carb problem. I have not tried pulling a spark plug one at a time yet, no.
We had this motor broken down quite a bit and went through a lot, replaced all gaskets and checked the piston rings as well.
I’m just confused as to why we have to set it run really lean in order to get it run at full throttle. If it’s too rich, the engine will idle fine, but at full throttle only run about 1/2 of that.
 
Just a quick follow up, I removed the slow speed adjustment needle and found that the little nylon bearing was brittle and broken into small pieces. I used a small wire to loosen them and tapped the carburetor so they would all fall out. I am getting another nylon bearing to replace it.
Could that have caused the problems we have had with motor not wanting to run at full throttle?
 
That's your low speed jet (idle jet) that supplies gas until the butterfly opens to a certain extent then your main jet pics up. What other issue were you having?
 
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