How do you set the carburetor on a mercury 4 hp motor?

Answer 1

If it has 2 jet needles the bottom should start at one turn out after gently screwing it all the way in until it stops. This is the low speed adjustment. The top on should one and a half turns out after gently screwing it all the way in. Motor should start and run pretty good. After it warms up after about 5 minutes or so. You can slowly adjust the low speed in or out where it runs the best at 1/8th turns and waiting about 10 seconds for the adjustments to take place. This should only be done around idle speeds. Do the same for the high speed with the motor going wide open and in gear. Should be done in a barrel full of water. If there is only one adjustment screw this is the low speed adjustment. If it doesn't start after initial setting some thing is wrong or dirty in the carb.