Mercury 9.9HP , 2002 4-Stroke carb leaking gas from top vent every other time

[GeorgioP]

Hi All, New to the Forum, but wanted to ask for some advice....

I was looking for some guidance after rebuilding my 2002 Mercury 9.9HP 4-Stroke carburetor using a Mercury carb kit, including new float, needle valve, float gasket, inlet filter, O-rings, and upper gasket.
The carburetor leaks gas from the top vent when primed and sometimes not, but when installed onto motor intake, then it leaks.
Also some days, it does not leak, then letting it set overnight, then will leak when motor is started after about 30 seconds after not leaking previously.
It also did this behavior last Fall, before the rebuild. The metal body and bowl only were soaked in Berryman's for 24 hours.
The idle and the main jet , thrust run great when the motor is running.
I also sanded down the edges of the float in case there was any sticking of the float to the carb bowl. The float height is within the 15.5mm spec according to the service manual. The tang is brittle white plastic and not very adjustable regardless, see picture below.
When the carb is built and empty, I can flip it and hear the float moving freely. The needle valve holds a seal on the seat when there is carb cleaner in the seat. the seat is brass and pressed into the body, The needle is the polymer tipped type, so I doubt there is much if any wear on the brass seat from this kind of needle tip.

I see many other Mercury 9.9HP 2001-2006 4 Stroke motors like this on other lakes in the area, so I am pretty sure others have ran into this issue. It's driving me nuts, as I've rebuilt other carbs in the past and not seen anything like this. I really don't want to have to buy an entire new carb just to fix the leaking.

The carb is very clean. Please let me know what you might suggest I do to repair. I am open to swapping out more parts etc..
Thank so much in advance.

George

 

[GeorgioP]

Hi Guys, even though nobody wrote anything here to assist me, I wanted to let you know what I found out was the cause of this problem after paying a certified Mercury tech to come over and take a look at my carburetor
The Mercury kit which they are selling on EBay, the float included in this kit is out of spec with the diameter near the idle jet.
The diameter of this generic white float (see above) is too large, so the top of the float is striking the carb intake body before the needle ever has the chance to seat fully and shut off the flow of gas.
These kits are so generic, sloppy, and unregulated, I guess that is the real problem.
You can tell if this is your problem, because the float clinks\contacts with the carb body, as opposed to bouncing from the rubber tip in the seat when the float height is being tested.
Since this kit contains the wrong float, hits the carb body, the carb leaks gas constantly and never reaches the proper height to shut off the gasoline. The other parts in the kit are correct and working , like the needle and the gaskets..
I wanted to let you know since Ebay vendors and others online keep selling these generic OEM kits, they are and will continue to cause others the same problems leading to expensive carburetor repairs and possibly worse!
Anyways..... the takeaway is that for me.....it's not leaking anymore, using the old, original, but yellowed 14 year-old float, and the new needle from the kit and other replacement parts from the kit..
Thank you,