2006 Mercury 9.9hp Carb Leaks Gas When Primed

[griffin.mac]

Hello All,

BACKGROUND: Last year I got a 2006 9.9 (0R132864) in a boat trade. It was very clean overall, ran a little rough, but okay. Since then i have replaced/tuned up many parts, including a thorough carb cleaning and fluids change, and now it runs great, when I can get it going.

PROBLEM: I noticed there was always gas below the carb, and often times I would see gas on the water when I was attempting to start the motor. So I took the cowl off and observed the carb while I cranked it up in the driveway. I noticed that when the I pushed the primer button, gas spit out from where the plunger cover meets the float bowl. Once I get the motor going, it runs great, but I noticed that maybe a drop of gas will drop from the same place every +/-10 seconds at idle. I usually have quite a tough time cold starting the motor, but it will always start on the first pull if I either a) just took out the carb (not cleaned, but took out and put back), or b) have been running it for a bit on the water (warmed up).

INTERVENTIONS: I replaced the old plunger which was slightly cracking, cleaned and reseated all gaskets in the plunger region. I thought a new plunger would take care of the problem, but it doesn't. The other two gaskets are in great condition so I didn't replace them.

QUESTION: Based off of my knowledge of fluids and small motors, I would think there would be a larger gasket between the plunger cover itself and the float bowl, but neither the manual or the mercury parts catalog have one listed there. Does anyone have any idea about what's going on here if it's not missing a gasket?

Thanks a lot,

Mac

 

[wn6ngp]

Not sure what a plunger is but it sounds like the valve that should seal off when the bowl is full is not working properly. Maybe the float level needs adjusting? There usually is a gasket between the top of the bowl and the plate that sits on top.

 

[flyingscott]

Is this a 2 strk or 4 strk motor? Mercury or tohatsu built? Put up a pic of the carb.

 

[Northeaster01]

Hi. Did you find the problem? I have the exact issue on the same year merc 9.9. Help please?
I have taken it apart and clean the carburetor out with seafoam it did not look very dirty or gummed up and the float and needle valve appear to move freely jets were clean with all or small orifices clear.
At first I also thought that there should be a gasket betweem the carb body and bottom diaphram/plunger and spring plate cover... but, upon looking further I think the two small o rings and the plunger/diaphram all make seals between the plate and body and therefore should contain the gas to stay in the proper places to flow.

 

[tommarvin]

hey, remove the carb,
watch all the you tube videos on carb/cleaning and rebuilding. before you tear your carb apart like on you tube,
pour your favorite beverage, take a chill pill and focus. you can fix the carb problem.
If your boating program can afford a used four stroke EFI you should buy it.and stop the carb BS problems..

 

[Northeaster01]

Hi - yes, watched all kinds of youtube videos and as mentioned above - took carb off and apart - needle valve and all jets looked great but soaked carb and parts in seafoam anyway and reassembed - still leaking at same spot.
I was thinking it may be a bad diaphram/plunger not sealing properly (even though it looks good) but since the OP changes his with no difference, I would love to know what he found in the end.. in Canada, my local dealer wants $75 for the diaphram.. I will take apart again today and perhaps connect to prime line with carb partially apart to see if it will start to fill without leaking or if it leaks no matter what position the float in in....
Feel free to give additional advice please!

 

[Northeaster01]

update - i just took the bowl / float assembly off and connected only the bottom carb body to the fuel lines and when i fill the bowl (with the main tank squeeze bulb) and then push the primer bulb, it still leaks alot between the bottom diaphram plates - therefore this rules out the float/ needle as being bad and not shutting off fuel properly and made me look closer at the diaphram and 2 O- rings that seal the bottom plate. When I popped out the 2 O-rings they certainly don't appear fat and round but seem quite flattened and harder than new ones, so I am leaning heaving to them being the culprits - can't likely get one today being Sunday but will try it with new ones next weekend.

 

[GA_Boater]

Northeaster01 You hijacked an old thread. Please start your own thread.

Closed.