no idle 50 hp 4 stroke 2004 outboard

[jan joyce]

Is there a history of problems with #4 carbarator for 50 hp 4 stroke 2004 Yahama outboards? Cannot get a new #4 carbarator to idle causing rough running sound. What can be problem(s) and how do we fix it? Thanks.

[boscoe99]

The #4 F50 carburetor is no more problematic than any other Yamaha carburetor. Probably better than most F40B carburetors.

Are you saying that the motor is running no better with a new #4 carburetor than it ran with the original #4 carburetor?

Has a compression check been done to ensure the number four cylinder is mechanically sound?

Have you verified that that are no intake leaks aft of the #4 carburetor? There are several paths for a leak to occur. Who knows what Yamaha was thinking.

Assumption is that you have an equivalent spark to #4 as to the other three cylinders.

[rodbolt17]

also was the fuel system cleaned prior to replacement?
was it set up using a 4 channel manometer and the correct service manual?
every thing syncs to #4.

[jan joyce]

yahama 50 hp 2004 idle problem

Thanks for the information. What is happening is the other 3 carbarators idle fine but the #4 makes a stuttering or rough sound and is not idling.

It is getting the spark.

[jan joyce]

idle problem with #4 carbarator Yahama 50 hp 2004

Fuel line was checked. Will recheck compression. How do we synchronize all the carbs with the #4? That may be the problem. Thanks so much.

[jan joyce]

idle problem with #4 carbarator Yahama 50 hp 2004

Did check fuel line. Spark is good. Rechecking compression. How do we syn the other carbs with #4? Thanks so much for your help.

[boscoe99]

Connect a tachometer to the motor.

Connect a manometer to all four of the carburetors.

Start and warm up the motor. Using the idle speed screw on the number four carburetor to set the idle RPM to 1000.

Note the vacuum reading on the manometer for the number for carburetor.

Set the vacuum reading for the number 1 ~ 3 carburetors to the same vacuum reading that was seen on the number 4 carburetor.

Set the idle RPM to 850 RPM's plus or minus 50 RPM.

[jan joyce]

idle problem with #4 carbarator Yahama 50 hp 2004

Thank you. Will try and let you know.