Help with merc carbs

[tonyaus]

I have a 70hp Mercury 1979. 3

I have a 70hp Mercury 1979. 3 cylinder twin carb.
Carbs were flooding after it sat for 2 years. Carbs were removed cleaned and new inlet needles and seats fitted. Float levels set exactly as per the manual. Started motor motor ran fine for 10 mins then it starting coughing and spluterring. Removed airbox cover to find top carb flooding. Have reset float level since replaced float and lever. Top carb still floods. Fuel also comes out of vent jent when primed. Please help.

Stumped

 

[tonyob]

"Tony,

I have had this prob

"Tony,

I have had this problem a number of times. It always seems to be Mercury carbs when it happens. All I can say is that you can bet that the inlet needle is not seating properly, or it is defective. I keep about ten of these assemblies (needle and seat) on hand for such times. I just replace them until the carb stops flooding.

You can try adjusting the float level a bit, just to insure that the float is closing the valve. Set the float height according to specs, then change it so that the float does not rise up as high with the valve closed. This tiny bit of difference will not really affect the fuel supply.

Another thing you might look for is debris in the fuel. Sometimes tiny pieces of gasket, fuel pump diaphragm, or fuel hose get caught in the seat and interfere with the operation of the valve.

Make sure there is nothing interfering with the motion of the float, preventing it from rising up completely.

Also, make sure you have installed the washer under the seat. This is important, but I have a feeling you have done this properly.

Tony"

 

[tonyaus]

Thanks tony i armed myself wi

Thanks tony i armed myself with another 2 inlet needles and seats and the second one did the trick. Had the boat out the motor ran great. Not happy with mercury though cause the original one i replaced should of done the trick. Could these have a fault when manufactured??

 

[tonyob]

" Tony,

I am convinced that

" Tony,

I am convinced that many of these are defective right out of the box. Since they used the same assembly for so many years I think they may all have been manufactured a long time ago, so that the tips of the needles deterioratd over time.

I have rebuilt Mercury carbs that worked fine, but after a short time, I had to replace the needle and seat because of flooding.

This has never happened with other types of carbs.

Tony "