20 hp merc flooding despite efforts to rebuild

[deejathome]

Help. PLEASE. 90 20hp merc, starts and runs, but floods out and starts to bog down. I take off the fuel line and it runs fine. Put it back on and it floods again. When I squeeze the primer bulb, fuel runs out the top of the carb. Ive changed the fuel line, float, needle, diaphragm, blown it out, AAARGH!! Tank is venting properly. The only thing I havent changed is the fuel line connection at the motor, (plug on the fuel line). Is this a factor? Could I have got a bad needle? Wrong size? Is the seat changeable? The first person who solves my problem gets a free day fishing trip on the red river in Manitoba!!!

 

[KCLOST]

Re: 20 hp merc flooding despite efforts to rebuild

Time for a carb rebuild.. Get the kit and the manual.... Fuel should not run out of the carbs...

 

[deejathome]

Re: 20 hp merc flooding despite efforts to rebuild

What the heck is left to rebuild??!!

 

[fishguts]

Re: 20 hp merc flooding despite efforts to rebuild

When you squeeze the bulb to prime the motor, does it go flat and stay that way? I ran into the same problem with my motor. I changed the bulb and fitting on the end of the hose (connecting the hose to motor). It turned out that something happened to the small connector. I changed it for $3 and all is well.

 

[jim dozier]

Re: 20 hp merc flooding despite efforts to rebuild

First thought like everyone else above is a float valve that isn't seating properly. You've apparently worked on the floats already. I don't know about your particular engine but I would think that the whole float valve including the seat would be available. Assuming that your work was primo, the other possibility is that you have a tear in the diaphragm in your fuel pump which is injecting raw fuel into the intake transfer port of the cylinder from which the pump receives its pressure pulse. This will cause that cylinder to run rich and kill the cylinder. A rebuild kit for the fuel pump is inexpensive and usually easy to install. Might take a look.

 

[deejathome]

Re: 20 hp merc flooding despite efforts to rebuild

Well, it seems Ive found the problem. I spent some time today rebuilding the carb, AGAIN, and this time I took an air line and small wire to all the journals and lines. It has cleared and is running now. Thanks to all. However, I will need to post a new problem as now it is popping or kind of backfiring at idle. Rev it up and it straightens out. If its not one thing its another I guess...

 

[jim dozier]

Re: 20 hp merc flooding despite efforts to rebuild

When a 2-stroke "sneezes" at idle your idle mixture is too lean. If you can't correct this with adjustments to the idle mixture screw, you will have to go back into the carbs to find out why it is running lean.

 

[deejathome]

Re: 20 hp merc flooding despite efforts to rebuild

That sounds exactly like whats happening. I know where the fast adjustment screw is, where is the idle screw? THX!!