What is causing the problem with our 3.5hp Mercury 4 stroke?

[RichardS]

I need help with the following: - I went ahead and cleaned the carburator, main jet, set screw, etc - all of it - and it starts right away at low setting, but the second I try to rev the engine, it just dies. I am able to run the engine in forward also only in the lowest setting.

I read somewhere the set screw is 1.5 turns - I have tried several things without success. I have not soake the main jet and main nozzle, but I have use plenty of carburator cleaner on it. I have not tried yet to clean the low air jet - i do not know how to paste in a message but is the one in front of the choke valve

It sounds as if you need to do a complete carb strip down and also clean and check the needle valve operation and the float height. Perhaps turn out the screw to more like 2 - 3 turns from fully in but I doubt whether that is the issue.

Richard

 

[macd]

the second I try to rev the engine, it just dies.

If the dying really is instantaneous, suspect the main jet first of all. As Richard writes, the screw position wouldn't seem to fit your symptoms.

 

[steve66]

Sounds like weak mixture either by a partially blocked main jet or from sucking air from your inlet manifold. Did you change the carb gasket?