Idje nozzle carb is set too rich
carburetor or spark plugs
A 1.9 TDI can hum at idle if the spark plugs foul. A clogged fuel filter can also cause this issue.
1978 80 Mercury Outboard IDLE ADJUSTMENT
You adjust idle with idle timing
outboard motor will start and idle, but dies out under load
It's my guess, and only a guess, that the idle jet is either plugged or the idle screw is turned in too tight. Judiously apply some carb cleaner and open the screw 3/4 of a turn. Once you get it running, play with the screw to smooth it out.
The Dodge ram 1500 rough idle can because by a bad spark plug or spark plug wire. The rough idle can also because by a bad camshaft.
== Is this engine the plastic cowling with idle knob and choke knob on the front pull it to choke and turn to raise idle? = Read more: http://www.justanswer.com/questions/1dpbt-25-hp-mercury-outboard-water#ixzz0HH1RenQM&B
For a 1977 Johnson 75 hp outboard, the idle timing should typically be set around 4 to 6 degrees before top dead center (BTDC). For wide-open throttle (WOT), the timing is usually set at about 20 to 24 degrees BTDC. It's essential to consult the specific service manual for your model to ensure accurate settings, as variations may exist based on engine condition and modifications.
The recommended idle RPM setting for a Johnson 150 outboard motor typically ranges between 600 to 700 RPM. It's important to consult the specific owner's manual for your model, as variations may exist based on the engine's year and configuration. Proper adjustment of the idle RPM ensures optimal performance and helps prevent stalling. Always make adjustments while the motor is in gear and in the water for the most accurate settings.
With mine, the rough idle was fixed by changing the spark plug wires.
To set the idle speed on a 1965 Mercury outboard, first ensure the motor is warm and running. Locate the idle adjustment screw, typically found on the carburetor, and use a screwdriver to turn it clockwise to increase the idle speed or counterclockwise to decrease it. Adjust until the engine runs smoothly at the desired idle speed, avoiding excessive RPMs that could cause stalling or rough operation. Finally, double-check the adjustment by letting the motor idle and observing its performance.