15 HP 2 stroke 2005 Yamaha outboard will not run at low speed

[ceeteemar]

2005 15 hp 2 stroke Yamaha will NOT run at low speed. Have changed the 3 jets , installed carb kit, soaked carb in cleaner for 3 days. Has spark, runs great at high speed.
What next?
At a loss
Capt. Jack

[TownsendsFJR1300]

Did you inspect the fuel pump (which is part of the carb) and fuel filter?

Was there any crap / varnish found inside the carb?

Any recent work done before it started acting up?

2005 15FMHS Yamaha Outboard CARBURETOR Diagram and Parts

[99yam40]

what jets did you replace and why?
Did you remove the pilot screws before soaking and cleaning?

lots of passages and ports to be cleaned.
Possible to have low compression, leaking seals(loss of vacuum)

[panasonic]

2005 15 hp 2 stroke Yamaha will NOT run at low speed. Have changed the 3 jets , installed carb kit, soaked carb in cleaner for 3 days. Has spark, runs great at high speed.
What next?
At a loss
Capt. Jack

Take carb apart again and blow out all passages with compressed air. Take a piece of stranded copper wire and make sure you can pass it thru all passages. Sometimes crap in the real small holes will only come out with wire poking. And also as noted check the fuel pump diaphragms or just replace them..they are cheap.

[Jason2tpa]

Sync and time? Idle screw adjustment?

[ceeteemar]

15hp 2 stroke 2005

The fuel pump three black diaphragm pieces were changed. The three brass valves and the float valve were changed. Everything that could be removed from the body of the carburetor was removed before soaking in cleaner. The compression is good. The plugs were changed. The top one looked normal but the bottom one was almost black with oil residue, not carbon deposit.
Ceeteemar