Yamaha /General Outboar Tuning question

[casual]

I have a Yamaha 40 Hp Outboard that ran great Last year. This year it starts and idles fine but at full throttle it gets bogged down and will not plane out or output to it's capacity. After removing the cover and playing with the Choke we found the boat Ran great with the choke in 2/3rds at full throttle.(Got up into the middle 30s as opposed to the 8-10 it was running before. What adjustments should I make? I didn't want to adjust the choke so that it is only a third open when set to full open. Would I want to adjust the needle valves on the carbs? Is it just getting too much air in the mixture? Should I go to a higher octane gas? Any help would be appreciated as I am not real familiar with outboards. I do know that I can't cruise around the lake with a buddy holding the choke 1/3 out all the time. Thanks in advance.

 

[Backlash]

Re: Yamaha /General Outboar Tuning question

It's time to tear down & thoroughly clean the carb(s). The fuel that's been sitting in there since last year has turned to varnish and is restricting fuel flow in the high speed circut. This results in the "lean" condition you're describing. If you're not comfortable with doing the job yourself, take it to a good wrench. Pretty straightforward job if you have a manual.<br />Backlash

 

[casual]

Re: Yamaha /General Outboar Tuning question

Thanks for the advice. Would it need this after just one year? Carbs were rebuilt last year and new lower unit put on as well. Carbs look like brand new. Is the gas your refering to, the residual gas from last year? (I mean I did use fresh gas this year.) I didn't want to start monkeying with it since it ran so good when I put her away last year without consulting more knowledgeble sources. Can motors get this out of tune so quickly?

 

[Backlash]

Re: Yamaha /General Outboar Tuning question

I'm not sure what procedures you went through when you put the motor away for the winter, but if you didn't use a gas stabilizer (Seafoam for example) and/or didn't run the fuel out of the carbs, the gas that sat in the carbs during the time the motor was laid up will turn to varnish and gum up the works. <br />Backlash

 

[rib fishin]

Re: Yamaha /General Outboar Tuning question

I have the same problem with my 115hp 1994 2 stroke yammie. Carbs cleaned and fine tuned last year and the boat ran great all year. I run startron in boat all year long and usually have no problems. This year big problems but I cleaned the carbs am now at about 85% but can not get any better, any suggesstions?
Max RPM around 4700 and low end bog when trying to shoot out of the whole.