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Dominick, Marine Mechanic
Category: Boat
Satisfied Customers: 1009
Experience:  25 Years Experience as Mechanic, 20 Yrs Boat Yard Owner/Mechanic, Factory Certified
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Mercury outboard motor float problem, how to adjust float on

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Mercury outboard motor float problem, how to adjust float on 2002 9.9 hp. Ser # XXXXX



Thank You for Your Question,


With the carburetor. body turned upside down, and all internal pieces in place (No Float Bowl) Hold carberator at eye level and check for the float to be level and straight in comparison to the carberator body. If this is good, adjust the level so that the gap between the float and the body is at 1/16th of an inch when looking directly from the side. Adjust by bending the float arm with a pair of needle nose pliers. Bend both arms as one and don't apply any pressure to the needle. Check again for straightness.


Also some good checks: The float is on correctly with the rounded edge up towards the body. / Check the float to be sure it isn't leaking by shaking and feeling for fuel inside of float / When the carberator is assembled fully, lightly blow air into the fuel line connection with your mouth and short piece of fuel line, flow should be impossible with the carberator. upside down and good flow with slight resistance right side up.

Be sure the carberator is clean, We soak all outboard carburetors with "Outboard Engine Decarbon Chemical" which won't hurt anything inside the carberator. and then wash off with soap and water and complete with drying off with compressed air.

Usually the problem I most often get is when a customer attempted to clean the carberator and missed one or two tiny passages. You can't spot clean it, disassemble completely and clean with the chemical. Don't remove any "Welch' plugs.

If you have any questions please don't hesitate to ask...



Customer: replied 8 years ago.
The float in my carbureator and the arms are plastic, how can I adust them, will it break them to bend them?


The picture I have for that serial number shows a Two Stroke motor and a metal float arm. Is the motor two or four stroke?

If it is two stroke, and there is no small metal tab contacting the needle on the float arm. If this is the case, there is no adjustment. Only the pieces must be correct and the arm installed correctly and the float will come out right...


Customer: replied 8 years ago.
The motor runs when the choke is out, but kills the engine when you push it in. At high speed it seems like it is running away from gas, at 3/4 it runs good with the choke all the way out. The previous message about the float and arms being plastic was my question also.


Ok, Lets take this from another perspective.

If the engine continues to run with the choke ON and won't with the choke off is a indication that the carburetor has blocked passages and needs to be cleaned throughly. The reason it will run with the choke on is the engine is getting its fuel from the choke system and not the high speed jet.

When you take the carburetor apart to clean take note to float setting before complete disassembly.



Customer: replied 8 years ago.
I understand, I still need to know since the float is plastic and the arms are also, it is one complete piece of plastic. How can I adjust the arms without breaking them. The carberuator has been cleaned but we will clean it again and will make note of the way the float is in the carbeurator.


If you could send a picture of the arms and float this will put the float situation to rest.

you indicated in your answer that the "float is plastic and the arms are also, it is one complete piece of plastic." I have no way of understanding how the float and the float arms are the same piece.

Is this your carb? Ser# XXXXX it is...the float arm is #29





Customer: replied 8 years ago.
The carbeurator number is XXXXX
Customer: replied 8 years ago.

I might not have told you this was a four stroke engine called a big foot.



Well That answers all my questions....

It should be the carberator in the picture below...If it is there is no adjustment to the float height....Just check the items above in the first two answers...





Customer: replied 8 years ago.

Dominick, Thank you for all your help, this is the right carb. I did not think there was an adjustment on it, but a Mercury repairman said there was an adjustment. I will clean it and blow it out like you said and hope that takes care of my problem. Merry Christmas!


Let me know how it goes and if you need any more help....


Merry Christmas...


When your ready please take a second to feedback...


Thanks Again!!!


I have noticed that you have not accepted my answer to your question. If you could do I would appreciate it...

Thank you Very Much!!!



Dominick and other Boat Specialists are ready to help you
Customer: replied 8 years ago.
I did answer that I accepted your answer, I had put $15 on account to pay and they said they would notify you. I just checked and they show 0 balance in my account. I don't know if I did something wrong or not. Customer


Seems that everything has gone through this morning....


Thanks Again,


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