Carb problems on 1994 Mercruiser 7.4 Thunderbolt V

[shellone]

Initially I had high fuel consumption, so I first changed the spark plugs and had the carb removed and maintained (Rochester Quadrajet, cleaned and repair kit applied). The accelerator pump gasket was stiff and did not close right (which we thought might be the cause for the higher consumption right there). Installed the carb, connected a separate tank to measure the fuel usage and here I ran into a problem. Priming took a long time and caused fuel to exit from the top of the stamp of the accelerator pump. Anyway the engine started without problems, ran smooth, the idle was higher than before the cleaning, but I ask myself: should I prime this engine at all (do not usually do it, but this time I wanted to prime the new carb)? And if I do, should the priming hand pump not become hard when the swimmer closes? Furthermore, I believed that if the fuel just 'runs through' the carburetor the engine should drown ... was I under a false assumption? Before taking the boat for a spin and check the consumption I would be glad to know whether the priming pump not getting hard indicates a problem or not, hope somebody can help ...

 

[alldodge]

Assuming the primer bulb is just for testing

Priming took a long time and caused fuel to exit from the top of the stamp of the accelerator pump.

The float level is set to high or the needle valve is not closing off the fuel when full

 

[shellone]

Assuming the primer bulb is just for testing


The float level is set to high or the needle valve is not closing off the fuel when full

Thanks so much for the fast reply ! If the float level is set too high or the needle valve is not closing ... would it spill fuel also while running, e.g. idling - or would it spill only when priming ?

 

[alldodge]

Yes, to both
I'm working off what you say, it leaked during priming?

Not leaking when running is the way it should be, but also should not leak when priming.

Note: the priming bulb will be removed when done, right?

 

[Grub54891]

A lot of those floats are the plastic type. They seem ok, but are saturated and to heavy. I’ve learned to just replace them. When it is running, look down the carb, you should see a mist, if there are any drips, it’s the float. It doesn’t show up when sitting.

 

[shellone]

Yes, to both
I'm working off what you say, it leaked during priming?

Not leaking when running is the way it should be, but also should not leak when priming.

Note: the priming bulb will be removed when done, right?

Yes, the primer was between secondary fuel and c-pump. Normally the hose goes from fuel separating filter (against water) to c-pump.

 

[shellone]

A lot of those floats are the plastic type. They seem ok, but are saturated and to heavy. I’ve learned to just replace them. When it is running, look down the carb, you should see a mist, if there are any drips, it’s the float. It doesn’t show up when sitting.

It only leaked while priming. While running, I saw the mist in the carb as you described. I'll ask the technician who cleaned the carb about the floaters, thank you so much for the hint !

 

[Lou C]

Are you using e 10 fuel?
If so some of the Orings for the accel pump will leak, there are better ones available, thru suppliers like Cliff's High Performance Quadrajets and Quadrajet Parts
There should not be any fuel visible around the plunger for the accel pump.
Another cause of sticking floats & needle valves involves the little clip on the float arm. If this is put in the wrong place (like one of the holes in the arm) it will cause the needle valve to stick.

look at this pic, see the float arm, the little clip that goes around the needle valve is at the top edge of it. that's how it's supposed to be....not in one of the holes...