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My 1999 Yamaha 40 loses power at wide open throttle. I have replaced all internal and external fuel lines, fuel filter, fuel pump, fuel tank, plugs, etc. Ball stays hard. The condition will correct itself if I throttle back, listen for the engine to surge, and then open it up. As an additional note, the stream of water comes out warm, whereas my 8hp runs cool. The local Yamaha dealer is stumped, suggesting $800.00 in repairs of the electronics as the next step. Any and all suggestions are greatly appreciated.
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Leeds,
If your motor has been allowed to set up for more than two months w/o being run, or if it has been at least three years since last carb overhaul, I would remove carbs, teardown, clean, and install a carb kit.
Good luck [img]smile.gif[/img] ,
Ken K -
Ken;
The local dealer "claimed" to have serviced the carbs at the last service this year. This engine is mothballed with fogging oil each winter, and used regularly in season. This is our second summer with the problem.
Thanks for the suggestion.Comment
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Leeds,
Sure sounds fuel related - like maybe a float in one of the carb bowls sticking.
You might try pulling the high speed jets and squirting some Berryman's Chemtool into the orifices. Also, inspect the ends of the jets - if they have o-rings that are cracked or distorted, replace them.
You also might try doing a shock treatment with Seafoam. Scroll down to my post to "CLL" dated May 27, 2005 for the procedure.
It could be an ignition problem, but that would be the last thing I would look at.
Good luck [img]smile.gif[/img] ,
Ken KComment
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Ken;
Looks like it is time for a service manual. I am much less dangerous when armed with the proper tools. By the way, this engine has been smoking a lot at startup. Is there a connection there?Comment
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Leeds,
Check the choke butterfly valve in the throats of the carbs - make sure it is returning to "off" position (horizontal) after crank-up. Maybe it is sticking partially closed after crank-up, and that is causing extra smoke. Could also give you problems at high speed.
I would recommend a Yamaha shop manual if you are going to get only one - go to www.yamahapubs.com for online ordering.
Good luck [img]smile.gif[/img] ,
Ken KComment
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