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1974 Evinrude 9.9hp

Jupiter Dinghy

Jupiter Dinghy

Regular Contributor
I got this non-running for about a year, motor, that I am trying to put back in use. After replacing the plugs that were not even close to the correct ones, measure the compression (at a healthy 110 on each cyl) I pulled the cord a couple of times and to my stupor, the thing started. Running ugly of course and throwing all kinds of exhaust trash in my test tank, but it was actually running as long as I kept the choke on, it would die as soon as I pushed the choke off. So I thought to myself it should be an easy fix with a carb rebuild, and proceed to the operation. The carb was actually not too bad, but some smell of old gas was there. Cleaned it real good in every orifice, put it back on with new gaskets, float and seat, and start the motor.
To my stupor, once again, it did the exact same thing as before I rebuilt the carb!!!! It runs as long as I keep playing with the choke, which acts as a throttle the more I pull it the higher it revs, but dies as soon as I cut the choke off. What should I look at next?
It sputters at times but always starts right up on a pull or two, so it feels like a carb issue. what do y'all think?
 
You're overlooking something within the carburetor. Clean the high speed jet carefully with a piece if single strand steel wire.

Adjust the slow speed adjustable needle valve as follows:

(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.

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.
 
joereeves said:
You're overlooking something within the carburetor. Clean the high speed jet carefully with a piece if single strand steel wire.

Adjust the slow speed adjustable needle valve as follows:

(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.

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.
Click to expand...

You know.... reading your post made me wonder if after all the focus and care I gave cleaning the carb itself, I didn't forget to clean the high speed jet and just put it back in there as it was!!! What an idiot..... well I earned myself another hour or so taking the thing off and putting it back in! The good news is I don't bill myself for labor. LOL
Thanks a lot for helping me think! Will keep you updated...
 
Bingo! You nailed it joereeves! I missed the high speed jet in the cleanup routine.
Got it cleaned now and the motor runs fine. Thanks for pointing me in the right direction.
 
Now here's the sequel: The motor starts and revs fine now, but after it warms up, it doesn't idle right. It sputters (like a mild backfiring mentioned above) and ends up stalling, and this despite any adjustment made on the slow speed needle. Going richer, or leaner makes no difference. So I did a bit of research online and found a user with a similar problem, and most responses pointed to a replacement of the coils....
So I grab good coils from another motor to check and see if it makes a difference, and now the darn thing won't start. Since I never replaced coils before I am wondering: Coils are "plug and play" right? There is nothing else involved when replacing them, or is there?
To eliminate the possibility of error in the wiring, I switched the top and bottom coil connections just in case, but no go either way.... Any recommendation?
Thanks again.....
 
Are the coils from a like motor?

Whatever, you say the slow speed needle makes no difference where you put it. It should. Or you have an air leak in the intake manifold or crankcase.

EDIT: ---OR--you still have a blockage in the carburetor's idle circuit.
 
Last edited:
Yes, coils are "plug & play" so to speak "IF" they are the identical ignitions system and wired properly.... ie you cannot install coils from a standard Magneto or Battery Capacitance Discharge system to a Magneto Capacitance Discharge ignition system.

Put your old original coils back on to see if your ignition comes back.
 
joereeves said:
Put your old original coils back on to see if your ignition comes back.
Click to expand...
That's where the enigma lies..... I did that and no start.
The coils I took came from same ignition system (74-76), and note that I do have spark. On both plugs.... I know the carb didn't clog again, as a matter of fact I started it and it ran fine (except for the idle sputtering) yesterday, when I decided to swap the coils.
 
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