F20 four stroke fuel/air screw setting

[DSmith1178]

I had to do a full rebuild on my F20's carb due to the needle valve being bad and flooding out carb. Before disassembly I counted the fuel pilot screw as 3 1/2 turns out from being fully seated. Thats where I set it upon reassembly. I bought engine used and thats where it was set. Engine finally is running better then ever at high speed but coming off plane and idling down it stalls out. Its not jets because I rebulit the carb and cleaned it throroughly. Im wondering if the fuel screw is the culprit as well as idle rpm speed. Does anybody have the correct idle speed rpm and is that measured in gear or neutral. Also, where should the fuel/air screw be set at....its a 2008 F20. Thanks!!

Dave

[boscoe99]

Would have been better if you told us exactly what F20 model that you have. An F20 may not be an F20 may not be an F20.

Idle RPM for some F20's is 1050 in neutral gear.

Idle mixture jet for some F20's is set 2 3/4 turns out from being lightly seated, plus or minus 1/2 turn.

[DSmith1178]

Sorry bout that.... Its a 2008 F20 MLH. Thanks for the quick reply!!

Dave

[rodbolt17]

you will find most carb specs in the manual say EPA since about 2005. I typically start at 3 1/2 then set the idle speed then play with the a/f screw in and out trying to find the point where I have to lower the idle speed to hit my target speed and repeat.
originally there should have been a tamper proof seal over that screw.

[boscoe99]

Sorry bout that.... Its a 2008 F20 MLH. Thanks for the quick reply!!

Dave

2 and 3/4ths turns outwards it is then.

[Tugboat6371]

I have a 2014 20hp 4 stroke and I have searched the web to find the correct idle screw adjustment, where might I find this info.

[boscoe99]

Need the complete model.

In general the setting is determined by how many turns it takes to screw the idle mixture screw inward until it is lightly seated. Then annotate your service manual to record the setting.

[Tugboat6371]

F20smha and I have looked for a service manual for this model but no luck, only for older models.

[boscoe99]

https://www.boats.net/product/yamaha/LIT-18616-02-96

[boscoe99]

2.75 turns outward from being lightly seated. Plus or minus 0.50 turn.

[Tugboat6371]

Awsome thank you so much