Mercury Classic Fifty flooding out sometimes.

[FloridaMan84]

Hello everyone. Great site! I'm hoping someone could help me out with this problem.

I have a Mercury Classic Fifty that is intermittently problematic.

If it sits for a week or more and you turn it on with the water hose adapter it will sometimes run very rough, smoke a lot, and not idle at all. When you put the throttle to idle position it will die immediately and some fuel will spill out of the front of the bottom carburetor once it completely cuts off (where the choke disc is). Sometimes if it is running at a higher RPM fuel will squirt out the top front-right opening above the choke disc until the motor shuts off. Nothing comes out of the top carburetor at all. I have also noticed bubbles in the fuel filter tube.

Now after trying to start it for a while unsuccessfully I will walk away and come back after a couple hours and try to start it again. THE INSTANT I turn the key and start to turn over the motor it comes alive and runs amazingly, and wont give me any more problems for the day, and no air bubbles in the fuel filter. I have been combating this problem by making sure to run the engine the night before and the morning of a fishing trip, with success (so far).

Something tells me this is some sort of fuel pressure issue since the bottom carb is the first one to get fuel, but I am no professional so this is just speculation.

This is what I have done to try and fix this problem so far...

-Rebuilt and cleaned both carburetors. New floats, needles, springs, gaskets.

-Replaced fuel line connector to the motor

-Made sure vent on gas tank is completely open

-Replaced old/worn looking fuel lines in the motor

If anyone has an idea what is going on I would greatly appreciate your advice. I would hate for this problem to ruin a good day of fishing!

Thanks for your time.

 

[Iceman66]

Re: Mercury Classic Fifty flooding out sometimes.

Time to check fuel-pump I guess.

 

[Georgesalmon]

Re: Mercury Classic Fifty flooding out sometimes.

And, you did set the carb floats exactly the right height, right? Just say'in.

 

[roscoe]

Re: Mercury Classic Fifty flooding out sometimes.

recheck carb floats, inspect reeds, rebuild fuel pump.

 

[FloridaMan84]

Re: Mercury Classic Fifty flooding out sometimes.

And, you did set the carb floats exactly the right height, right? Just say'in.

I set the floats to where they would put a little more pressure on the needles. The height the book told me was 1/32" and it put almost no pressure at all on the needles and fuel would just flow past them with the tenderest squeeze on the fuel primer. I can't imagine that would be the problem because it runs great otherwise and if fuel is already flowing uncontrolled past the needle now how would making it even lighter help?

 

[FloridaMan84]

Re: Mercury Classic Fifty flooding out sometimes.

recheck carb floats, inspect reeds, rebuild fuel pump.

Reeds look good.

I guess I'll go after the fuel pump next. Thanks for the advice.

 

[FloridaMan84]

Re: Mercury Classic Fifty flooding out sometimes.

Time to check fuel-pump I guess.

Will do.

 

[mixerjv]

Re: Mercury Classic Fifty flooding out sometimes.

(dup post)

 

[mixerjv]

Re: Mercury Classic Fifty flooding out sometimes.

By some chance, are you using a newer tank? You have the symptoms of the 2012 newer EPA tanks, that are under pressure until some 6psi builds up, even if you open the "vent" (which, 2012+, is not a true vent). It would explain why it runs horrible at first. A fuel demand valve is recommended for these new tanks to prevent over pressurization I think you're experiencing.

I have a 1985 classic Merc 50 4cyl and went back to the older tanks to solve the problem.