03 40TLRC poping / missing sound while running

[mobjack1]

Good moring, ths is my first post and I am the new owner of new to my family 03 40TLRC, I am experincing a poping or missing sound while the boat is running under load, it is on a pontoon by the way.

I have recently given the boat a tune up, replaced the prop, service, replaced the plugs and even took the carbs apart and cleaned them this last Labor Day weekend. the sound is still present. I have cleaned the fuel filter bowl as well. Everytime I take the toon out of the water I rinse the motor out with CRC Salt Away and remove the fuel line and run the motor until it shuts down from lack of fuel.

The sound is heard but I do not feel a shutter in the motor, after long runs it has a rough idle for a moment or so then clears up. I have recently started to use non- ethnoal fuel in the motor.

I hope the above description is clear to what the motor is experincing. Any help would be great!

[99yam40]

could be a lean sneeze with the pop description.
Could be the carbs still have a problem, might need to do a sonic bath clean.
Are floats set properly?
Might check fuel pump to see if it is leaking fuel into crankcase of #3,
but that would cause the cylinder to not light/fire properly do to too much fuel.

Did you follow all steps in service manual after reinstalling carbs for link and sync?

Compression, spark, and timing are all easy to test, just need proper equipment.
Coil ohms and voltage specs are in manual
Plugs wires and caps and maybe plugs could be a problem,

If all is good then you are left with fuel issues.

[mobjack1]

Thanks, that gives me some areas to check, I do have to get a manuel for the engine. I just cleaned the carbs and put them back on (droped the top cover and bowl and cleaned to the ports seat and float) and reinstalled and never turned any adjuster screws. I need to track down a manual....

once I put it back together it runs the same..

Should I get the manual from a dealer or a aftermarket version like the one listed below (is it worth it)?

Yamaha Outboards 2-250HP 1997-2009 Repair Manual 1-4 Cylinder, V4, V6, All 2 Stroke Models, Includes Jet Drives - Seloc 1703-IB - iboats