Logo
FULL SITE MENU

Nissan 4-Stroke 9.9 HP missing badly

M

mills

Contributing Member
Picked up a 2003 Nissan 4-Stroke Outboard. Starts on first or 2nd pull. Idles fine, but when u give it throttle it misses badly. Pulled the spark plugs and they are all black and sooty. Too Much fuel??? Pulled the carb off 4 X and cleaned it and it is perfetly clean. Everything seemed fine but I put in a new float valve just to be sure. Same thing. Starts right up and idles fine but misses badly whey you accelerate. Motor is very clean and looks like used very ltiile. Put a timing light on it and the spark advances very little??? Is the CDI bad??? Every time I pull the spark pugs after I run it and giver it throttle they are black and sooty. Need HELP !!!
 
You didn't mention model (year is irrelevant), but it's likely an MFS9.9B2. Did you disassemble/clean the accelerator pump?
 
Paul,
Thanks for your input. No model sticker is on the motor. Only sticker is the emmisions sticker. Based on the parts diagram, I think it is a MFS9.9B2. Disasemaled and Cleaned the carb 2 X but may have not have taken apart the accelatror pump. What number is it on the parts diagram? Sure acts like too much fuel being pushed into the cylinders??
 
What method did you use to clean the carb? 1-1-2 and associated are the accelerator pump plunger. There is a somewhat complex check valve system in the carb bowl for it.
002-21047-4_FIG05.jpg
 
Removed it, took it apart and ran small wire through all the small holes. Removed the small jet but did not remove the main jet (set plug in bad shape, but ran a wire through it) Also removed the top and cleaned that out. However, the carb was very clean when I first took it apart. Then put it in a solution of Gasoline and Seafoam, but I did not take apart the items you refer too. I will take it off again today and take apart the accelerator pump. Thanks again for your input.
 
Paul,
I don't have parts 1--1-2 or 1-1-3 on my carb??? Maybe that's the whole problem?? Attached is a pic of that portion of my carb. Thanks again.........
 
OK, great. I will order the Float chamber assembly part # [FONT=&quot]3H8032210. Looks like that contains all that I need. After I get it and install I will let you know how it runs. I "suspect" that the previous owner took apart the carb but lost or forgot to install the mentioned parts. Thanks again :)[/FONT]
 
OK, FINALLY got my motor running properly. Ordered a new float bowl chamber (3H8-03221-0) but this did nothing to stop the flooding problem. It did not contain the parts labeled 1-1-2 or 1-1-3 ??? So............ I bought a used carb on EBay and then the motor ran fine. This carb also did not contain parts 1=1-2 or 1-1-3 ???
However, the difference between the good carb and the bad carb was part # 1-11, the slow jet #42. On my old carb the whole in the jet was very large. In the new carb the hole was extremely small. Motor now runs fine with the new carb. However, when I put the new jet in the old carb, same problem???
 
Main jet was fine, clean and OK. Did not see a plunger?? None of the 3 carb bowls I had contained the parts you refered to..............spring and plunger???
 
The plunger normally is attached to the upper casting, so no, the bowl doesn't come with it. Since you have a good running setup, I would leave it alone.
 
Back
Top