Carb floods way too easily

[brooksk]

I have an '78 Mercury 800 80hp in-line 4 cyl, s/n 5004055 which has recently been flooding out intermitently every couple of days or so. Several times I have had to remove the plugs and dry 'em off, remove the dual carbs, drain and clean out in order to start engine. Once started the engine seems to purr at idle and runs like a top at WOT. I thought my starting problem was gone after these results but then it came back next day. The carbs seems flooded as there's gas around the throats and all smells gassey. Could my float be set too high and/or needle 'n' seat need not working. I rebuilt both carbs last fall and carefully adjusted the height of the float to specs. I haven't noticed any foreign material inside the carb or joints/hinges sticking. Both needles seems to move up n down easy, too. The electric choke seems to turn on/off okay. When I attempt to start I always connect the line and make sure to prime the bulb to firmness.<br />Any help would be appreciated.

 

[Yepblaze]

Re: Carb floods way too easily

What you describe as flooding can almost allways be attributed to needle seat area. <br /><br />Although I have seen, poor and or binding actuation, wet heavy or leaking floats, or where a cracked or otherwise internal leak has caused the issue although that is extremely rare.<br /><br />It's usually attibuted to foreign material in the needle seat itself. Doesn't even have to be a visible sized item.<br /><br />So I would suggest you change out the needle/seat(s) also take the floats and was down with a fast drying solvent. Dry them then set them in a warm well lit area while looking for any seepage indicated porosity.<br /><br />Also make sure you have good filtration of the fuel. You may want to ad an inline fuel filter.

 

[brooksk]

Re: Carb floods way too easily

Thanks Yepblaze!<br /><br />I happen to have another new needle/valve assembly I could install after cleaning the carbs out. Funny thing, you mentioned foreign material as being a potential culprit. All my whoas came after I discovered silicone particles/chunks plugging up my lines. I only changed out the lines but never the gas. Could be some bad or dirty gas re-plugging the needle area? I will install an in-line gas filter and change out the old gas.

 

[The Marine Doctor]

Re: Carb floods way too easily

Does this problem surface after running the engine...or after it has sat for a while?<br /><br />Do you disconnect the fuel when not in use?<br /><br />TMD

 

[brooksk]

Re: Carb floods way too easily

It was occurring next day or after motor was shut off. I just finished replacing the needle/seat assembly and double-checked the float levels. Bottom float was too low. Both needles had a rubber-like tip, like an eraser. New needles were solid metal and cone shaped. After re-installation, motor fired up and ran great. My shut down included disconnecting the fuel line first, letting the motor die out, then shutting off engine. Next time at boat I carefully primed motor and it started right up and ran great.<br />Could my priming method/bulb be flooding the carb or is it likely that the old needles were shot? I'd like to know as now I'm paranoid about how much gas to give her on startup.<br />(Also added inline fuel filter to keep carb clean.)

 

[mellowyellow]

Re: Carb floods way too easily

my '70 1150 inline 6 can (almost) never get enough gas...<br />except when the float sticks. lil tap on bowl<br />will normally free it up if it's otherwise ok.<br />pump bulb and see if gas leaks out of the front<br />of any carb. that's why they have check valves.<br />good luck,<br />M.Y.

 

[The Marine Doctor]

Re: Carb floods way too easily

If you leave your engine hooked up to the gas...in a HOT area its possible that the tank pressurizes and pumps fuel into the carb.<br /><br />Release any pressure off the fuel tank before connecting the fuel line. Again in hot weather if the tank is not vented it will pressurize.<br /><br />TMD

 

[Yepblaze]

Re: Carb floods way too easily

If you have little bits of debris in the fuel system it will reak havick with the fuel pump check valve(s) and carb needle/seats till you stop it's entry through the system and keep checking/cleaning, or replacing the aformentioned components.

 

[rabidfish]

Re: Carb floods way too easily

What kind of particles? Older Mercurys are notorious for have the inside of the fuel lines come apart & plug the system. Any "good" carb overhaul will include replacement of the lines & overhauling the fuel pump as part of the job. As a Mercury tech for over 20 years i can also say replace the floats if there is any question. Make certain the spring in the top is the correct height also (3/16 inch). If your needle has a spring in it, discard them for "solid" needles. This will take the variables out of thefloat height adjustment. Good luck!

 

[brooksk]

Re: Carb floods way too easily

I should clarify - the 'old' way of my shutting down was simply to turn off the key, tilt the motor and, half the time, disconnect the fuel line. I can see now how pressure in the lines from a 'hot' tank could cause additional fuel overflow. I'm trying to burn down some, if not all, of the gas in the carbs after disconnecting the line first before I shut down. Even though my tanks - portable and fixed - have vents, I suspect I was overpriming the carbs prior to startup.<br /><br />I did replace the floats and reset the height to manual specs, too.<br /><br />My needles don't have any springs, nor do the floats - gravity only.<br /><br />As for particles - I haven't noticed anything suggesting the line has deteriorated but if it has it would would most likely be from the motor's connection forward as I replaced the preceding lines and tanks. The fuel pump has been operating fine so I haven't replaced that yet.<br /><br />Hope all that info helps? I've picked up quite a few good pointers which are really helping out a lot. Thanks!