2007 Yamaha 9.9 High Thrust have to run on choke - SailNet Community
 
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2007 Yamaha 9.9 High Thrust have to run on choke

Hi folks,

A bit at wits end here.

I've cleaned the carb about 5 times, main and slow jets. Fresh fuel. New spark plugs.

I can start it up with the choke out, however, when I push in the choke it dies. It briefly runs faster when I push in the choke, then it slows down, thrashing about, sputters, and then dies. I've also tried pouring in sea foam.

I'm assuming the problem is the fuel mixture is too lean when I push in the choke.

Is this a vacuum leak issue? Is there an easy way to figure this out? Any good diagnostic tips to test what the problem might be?

Many thanks!
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Re: 2007 Yamaha 9.9 High Thrust have to run on choke

Sounds like not enough gas is getting to the engine. Silly question have you checked the pressure relief on the gas tank is working and if the gas line is widely patent and fittings work? Sounds like you already checked the common things that could limit fuel flow in the engine itself.

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Re: 2007 Yamaha 9.9 High Thrust have to run on choke

The carb must have a mixture adjustment. Have you tried to adjust? Most have a process where you tighten them down fully, then back out a defined number of turns and adjust from there. Do have the tech manual? Iím sure itís online, if you donít.

Another random thought is whether idle speed is set properly.


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Re: 2007 Yamaha 9.9 High Thrust have to run on choke

Thanks for the replies, folks.

I did tear apart the fuel pump, but other than being a bit grungy it seemed ok.

I opened up the carb again, and one of my jets had come loose. Guess I didn't put it back together properly.

She's running pretty smooth now. There's a slight hickup when I full throttle her, but nothing serious.

I spritzed quite a bit of carb cleaner into the air-intake as well.

I filed down the needle a bit as it felt like it might be sticking.

Also, when I put the carb back in I didn't screw it back in tight enough I think. It was leaking a bit.

Lessons learned: rebuild carbs very carefully, putting everything back in the same situation it was as you were tearing it down. Use clean fuel, clean everything, especially the jets. Make sure the needle isn't sticking. Make sure you prime the engine with fuel (duh). Cleaning the fuel pump might have helped, hard to say. Tighten all screws appropriately.

I don't know exactly what fixed it, but there you go. I did go from barely running to running 95%, so I'm pretty happy.
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