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Author	Topic:   1999 Yamaha 3-HP
motorhenry	posted 12-10-2011 07:33 PM ET (US)         [My 1999 Yamaha 3-HP outboard] motor now only runs when working the choke. It will not run with the choke off; it only runs on half or full choke. I cleaned the carburetor, gas line, and all in great [condition]. This motor has only about [five hours of running time]. Hope some one can help me [diagnose the cause of the problem that makes the motor only run when the choke is applied]. Thanks Henry
frontier	posted 12-10-2011 08:11 PM ET (US)             Exactly what happen to us on our small Yamaha outboard this year.[The cause of the] problem [is] Government-forced [blends of] ethanol [and] gasoline. Have a pro clean the fuel system and put in Sta-Bil treated gassoline. My local mechanic does about five a week.
jimh	posted 12-11-2011 09:22 AM ET (US)             Typically the choke causes the fuel:air ratio to increase. If the motor only runs when the choke is applied, the most reasonable inference is the fuel:air mixture is too lean in the normal setting. In a carburetor fuel induction motor the fuel:air mixture is typically determined by the size of the fuel metering orifice or "jet" in the carburetor. On outboard engines with low horsepower the diameter of the orifice can be small, and the orifice may be partially blocked. The usual recommendation would be to have the fuel system checked for obstructions or residues that were blocking fuel flow. Since you have already cleaned the fuel hoses and carburetor, you have already applied that remedy.
contender	posted 12-11-2011 02:51 PM ET (US)             motor; I had a 4 stroke 4 hp Yamaha, and as frontier stated it was the ethanol causing the block on the jet. It was a simple carb. and I was able to fix it each time, but got tired of it and got rid of the 4 stroke. I spoke to a guy that just graduated from one of these outboard schools in Fla. He stated yes it was the ethanol causing the blocks and other problems with the outboards (especially the small 4 strokes) and the best thing to do is disconnect the fuel line (shut it off in your case) and let the engine run dry.
wezie	posted 12-12-2011 09:29 AM ET (US)             Please forgive the question. Did you clean the tank and throw away the old gas?
motorhenry	posted 12-12-2011 12:20 PM ET (US)             Thanks for all that info. I fond that the small #40 jet pluged off. The first I just cleaned it and did not check the jets.Henry

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