50 hp merc surging 2000 model 4 stroke

[goblerblaster]

I have replaced fuel lines, fuel filter, gas tank connector, gas line to motor connector, fuel pump, run a can of Seafoam thru it, a half can of B12 thru it, a dose of Merc Fuel system cleaner thru it, and it still surges. It will idle all day long. It runs pretty good at WOT. Between 2500 and 3500 rpm it starts surging It will go from 2500 to 4500 without touching the throttle. Then it will go back to 2000 or 2500 rpm. I can/t find any loose fuel lines or vacuum lines. Plugs look good. Seems like it is getting air in the lines, but I am at the end of my skill set.

​Any suggestions? Gas is brand new. Any suggestions appreciated.

 

[ondarvr]

Try squeezing the primer bulb when it's acting up, this will eliminate an air leak or weak fuel pump, the next step it cleaning the carbs.

 

[GREE]

I had a similar problem with my Evinrude it ended up being the aftermarket fuel filter I put on my fuel line the fuel filter fitting where plastic and bigger diameter then my house and I could visually see air bubbles so i replaced it with another fuel filter and made sure to get the right diameter fitting to hose.

 

[goblerblaster]

I have squeezed the bulb while the engine is running and it has no impact. I checked the fuel filter lines and they are not leaking. Thanks for the replies.

Anyone else got any ideas ?

 

[ondarvr]

Well then, it's clean the carbs time.