Mercury 650 carbs rebuilt but still leak. Is this normal?

sutor623 · Feb 17, 2012

So I rebuilt both the carbs on my '67 4 cylinder 650 and they are both leaking. Is it normal? I know there is a tray to catch the fuel when you tilt the motor up, but right after I prime the motor it starts leaking. I changed all the gaskets that came in the carb kit. In the photo here you can see the little post that has a slit in it underneath the carb is where it is leaking. It is the throttle spring lever post.

merc850 · Feb 17, 2012

Re: Mercury 650 carbs rebuilt but still leak. Is this normal?

Did you set the float lever heights?

sutor623 · Feb 17, 2012

Re: Mercury 650 carbs rebuilt but still leak. Is this normal?

Yes the floats are new and the levers are set to factory specs. It never seemed to leak when it was running, only right after I primed the gas. I do not want to go and install everything yet if I will only have to disassemble again....

sutor623 · Feb 17, 2012

Re: Mercury 650 carbs rebuilt but still leak. Is this normal?

Anyone know what the deal is with this? I am waiting to finish installing the rest of the components cause I dont know if I need to do a full carb hardware overhaul.

Laddies · Feb 17, 2012

Re: Mercury 650 carbs rebuilt but still leak. Is this normal?

It is not uncommon with a good primer bulb to be able to overcome the inlet needles

sutor623 · Feb 17, 2012

Re: Mercury 650 carbs rebuilt but still leak. Is this normal?

Laddies said:
It is not uncommon with a good primer bulb to be able to overcome the inlet needles

Okay thanks Laddies. I still feel like some fuel is leaking through where the throttle plate hinge goes into the carb body. Even with the motor 100% level the fuel seems to drip right out of the spring hinge under the carb body. Is there a possibility that some fuel is leaking through there?

Laddies · Feb 17, 2012

Re: Mercury 650 carbs rebuilt but still leak. Is this normal?

If fuel is leaking into the throat of a side bowl carb at rest then the fuel level in the float bowl is high.

sutor623 · Feb 17, 2012

Re: Mercury 650 carbs rebuilt but still leak. Is this normal?

Laddies said:
If fuel is leaking into the throat of a side bowl carb at rest them the fuel level in the float bowl is high.

Okay so do you think that I should adjust the lever in the float bowl? It doesnt seem to leak in there at rest, but after I prime the engine, even if the fuel does not leak out of the front of the carb (like it would if too much came out) fuel still makes its way out of the bottom of the carb, seemingly right at the throttle arm linkage.

phebus1 · Feb 17, 2012

Re: Mercury 650 carbs rebuilt but still leak. Is this normal?

Mine have always done the same thing

sutor623 · Feb 17, 2012

Re: Mercury 650 carbs rebuilt but still leak. Is this normal?

phebus1 said:
Mine have always done the same thing

Okay, thanks Phebus. That is good to hear, because I spent a lot of time and did things EXACTLY how the manual stated. I guess I will just start putting everything back together. There is a tray that sets under the carbs with a hose from it that is designed to catch the extra fuel when you tilt the motor. Guess they just couldn't figure out a way to keep things dry back in the late 60's.

Faztbullet · Feb 18, 2012

Re: Mercury 650 carbs rebuilt but still leak. Is this normal?

Tweak the level just a tad to shut fuel off a little earlier as what your see is a float height problem. The fuel you see is coming from center discharge tube and running to rear of butterfly shaft. This wont effect running much except you could hit some rough water at lower speeds and could cause a stumble . Also get rid of those dang hose clamps and use the fuel injection style clamps as they pull a perfect 360? and will not cause a leak or damage hose, it looks like you got hose material coming thru the acme threads of clamps already.....

sutor623 · Feb 18, 2012

Re: Mercury 650 carbs rebuilt but still leak. Is this normal?

Thanks Fazt, this is what I needed to hear. I had a gut feeling that something was not as it should be. I do not want fuel running down my motor, or into the water during a fishing trip. That is why I have put the rebuild on hold until I got a better answer on here. Also, this sentence confused me a little.....

Faztbullet said:
it looks like you got hose material coming thru the acme threads of clamps already.....

jbcurt00 · Feb 18, 2012

Re: Mercury 650 carbs rebuilt but still leak. Is this normal?

I suspect that he meant the 'ladder' like spaces on the clamp have started to 'bite' into the hose, as if slightly over tightened to try & prevent fuel leakage. Probably leading to premature hose failure at the clamp......

phebus1 · Feb 18, 2012

Re: Mercury 650 carbs rebuilt but still leak. Is this normal?

I havent found those fuel injector style clamps in stainless. Would the zinc plated be fine for fresh water use?

Also, from my observations, people tend to pump the primer bulb harder then necessary. Pumping until just firm is fine, it doesn't need to be pumped hard as a rock.

Faztbullet · Feb 18, 2012

Re: Mercury 650 carbs rebuilt but still leak. Is this normal?

Would the zinc plated be fine for fresh water use?

Will work just fine...

sutor623 · Feb 18, 2012

Re: Mercury 650 carbs rebuilt but still leak. Is this normal?

Hey Fazt, thanks a lot for all of your support, from my L/U up to the carbs. The factory says to set the float levers at 13/32". I set them at 7/16" (14/32") and they now do not leak a single drop, even if I over prime them just a bit. Those float needles are setting good and tight!! I am ready to start installing the rest of my components. Thanks again man. You da man!!

Mercury 650 carbs rebuilt but still leak. Is this normal?

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