1974 Evinrude 9.9 won't idle at low RPM, need help

[hotpickle]

So I will start off with the warning that I'm not mechanically inclined. This motor has been my effort to learn how to do this stuff. I have learned a ton off forums like these and accomplished a decent amount on my own, but have come across a problem I need help with.

I picked up a 1974 Evinrude 9.9 at the end of last summer in decent shape, ran rough. The throttle has to be up for it to run. As soon as I try to bring the RPMs down, it sputters out and dies. I find that in order to get it to start I really have to rev it up. Also, it runs best at 1/4 choke. I played with the idle needle adjustment first, but it didn't fix the problem. I pulled the spark plugs... They looked ok to the untrained eye. One was a little black, but i cleaned them up pretty well i think. After reading FAQ's and other established threads, all signs pointed to a dirty carb. So I pulled it apart today, but it was spotless. Not a spot of carbon in it (I should point out that I got lucky and this motor is in very good condition... Everything is very clean, there is no corrosion or other sign of wear. There is no seeping oil).

One thing I did notice when the carb was off, was that the float was slightly off of parallel with the carburator body. I fixed that (the float was updated by the previous owner, apparently. Black plastic, clean no cracks). There was no corrosion or pitting in the float bowl (it's the metal fuel bowl). I put everything back together (including backing out the needle 3/4 from lightly seated) then reassembled the motor. There was a definite difference in running it and adjusting the idle, but it still has the same problem. When I try to throttle down and drop the RPMs, it sputters out and dies. It also makes sounds like it's backfiring (i don't know if that is what people are referring to as "sneezing"?). However, at higher RPM, it does run smoother and longer than it did before. I can scale the choke back a bit more as I adjust the idle, but I can never get it to the point where it runs without choke. I replaced the gaskets on the carb, so I am hoping I have ruled out the possibilty of air getting drawn into the carb from the seals.

I'm sorry this is long winded and probably confusing, but I have a video of how it runs after I put the carb back on today

https://youtu.be/VVpcXpjQZIE

Can anyone point me in the right direction on this? I apologize if this seems easy to the seasoned vets but I'm trying to figure out how it all works.

 

[ondarvr]

I didn't watch the video, but the low speed circuit is still dirty, needs another cleaning, it can take a couple cleanings before it runs right. There should never be any carbon in the carb, but every tiny passageway needs to be spotless. And the low speed needle is adjusted until it runs correctly, this may not at the suggested starting point, that just a point where it should start and run well enough to dial it in.

 

[hotpickle]

I didn't watch the video, but the low speed circuit is still dirty, needs another cleaning, it can take a couple cleanings before it runs right. There should never be any carbon in the carb, but every tiny passageway needs to be spotless. And the low speed needle is adjusted until it runs correctly, this may not at the suggested starting point, that just a point where it should start and run well enough to dial it in.

Low speed circuit. So is this what I am cleaning behind the small lead plugs?

 

[oldboat1]

Don't remove the lead plugs. They are left over from the manufacturing process.

Think this is probably the standard instructions: http://forums.iboats.com/forum/engin...eeves?t=167352 . To clean, it's best to fully disassemble, and soak all metal parts. I use lacquer thinner. Some use PineSol. The object is to cut through any varnish from old fuel, in all the smallest places (varnish, not carbon). I use soft wire or mono to clean every opening, including the little ports on top under the aluminum plug (That's the low speed or idle circuit). Then blow it out with carb cleaner.

To set it, start with 1 1/2 out (counterclockwise) from seated for the needle (low speed). The high speed jet isn't adjustable on yours, but must be clean. Your carb may still need some cleaning, but try first to dial it in. Try to start it at the initial setting, and warm it up. Then adjust clockwise 1/8 turn at a time -- rpms should increase at some point, and will want to throttle down with the twist grip. Keep adjusting the needle clockwise until the engine gives you a light backfire (lean sneeze) or stalls, then back it out counterclockwise about 1/4 turn. That should give you about the right adjustment for running. Make sure it throttles up and back without stalling, and goes into smoothly into gear at idle speed (technically, about 650 rpms).

You may have more than carb issues (fuel pump, potentially), but I would start with the carb and see if you can get it running smoothly. You should not need to choke keep it running (btw, if warmed up but using the choke to run, try the fuel bulb -- if successful, indicates a fuel pump issue.)

 

[OptsyEagle]

The slow speed circuit is under the welch plug (about a 1/2" diameter metal plug at the top of the carb, that you carefully punch through and pop out) and in the orifice for the needle that gives you the rich/lean adjustment. Did you replace the little plastic bearing inside the slow speed jet orifice? Looks like a very small plastic funnel.

Also, check your carburetor synchronization. When you increase throttle there is a metal plate (throttle cam) that turns and makes contact to the little roller on the carburetor. On that throttle cam is an indented arrow. That arrow should be in the middle of the carburetor's roller JUST when the cam hits the roller. Any adjustment is done by loosening the two little hex nuts on the starboard side of that cam, just under the flywheel.