Choking Problems - Yam. 90HP

[liamtovey]

I have a Yamaha 1997 3 cylinder, 2 stroke 90hp AETO. <br /><br />The engine only starts if the choke lever is opened completely. To get the engine in to gear, I have to slowly close the choke, then quickly push the engine into full throttle. Otherwise it dies, and I have to restart. Once in full throttle, I can back it off without the engine dying. <br /><br />Any ideas would be greatly appreciated<br /><br />Thanks<br /><br />Liam

 

[jim dozier]

Re: Choking Problems - Yam. 90HP

It is unclear from your description whether you mean to say that in order to start it you have to choke the engine (close the carb choke butterfly) and release the choke to run it (open the carb choke butterfly). Either way your idle mixture sounds like it is incorrect. Perhaps you can further clarify.<br /><br />If the engine needs the choke butterfly closed for a warm start the engine idle mixture is probably too lean and you should enrichen the idle mixture screw. If that doesn't help, you may need to clean/rebuild the carb with focus on the idle circuits. Choking the engine enrichens the mixture temporarily by increasing the vacuum in the carb and reducing the air flow.

 

[bonitoman]

Re: Choking Problems - Yam. 90HP

Your choke system is different that most systems with choke plates in front of the carbs. You have a pump that is connected to the middle #2 carb. I do not understand your question. Are you turning the switch on the choke on the middle carb or pushing in your key on the console to choke it?

 

[rodbolt]

Re: Choking Problems - Yam. 90HP

hello<br /> does your engine have a choke or is it primestart?<br /> in the US all 90's are listed as having primestart. it is possible someone turned it off or unplugged it. or it may be malfunctioning. if it has primestart and the warmup lever is raised the system will not work resulting in extremely hard starting. does the center carb have a little red plastic tag on it someplace that says open and manual ?<br />good luck and keep posting

 

[liamtovey]

Re: Choking Problems - Yam. 90HP

Thank-you all.<br /><br />I'm pretty sure that it is the red tab that is causing the problem. I will check in a week or two when I get back to the boat. We moved it when we got stuck about a month ago. <br /><br />Thanks<br /><br />Liam

 

[butlp]

Re: Choking Problems - Yam. 90HP

Liam,<br />Are you sure you are operating the choke on your motor? I re-read your post and thought you may be using the fast idle/warm up lever to start the motor. To start my Yamaha 90 I lift the fast idle/warm up lever 50%, lift the choke switch and at the same time turn the ignition key. When the motor starts I release the choke switch momentarily, but if it starts to die, put the choke switch back on. Depending on the temperature I may have to do this two or three times until the motor will run smoothly at a fast idle. I normally let it run at 1500 to 2000 rpm for a few minutes as I get the gear ready, but then I reduce the warm up lever and the motor idles fine at 800 rpm. If your motor will not idle without the warm up lever, then you need to check the carburetion, timing and perform the routine service as outlined in the work shop manual. If you don’t have a manual, I strongly recommend that you purchase the Yamaha service manual for your motor, it can save you a lot of money and down time.