high altitude jets needed. ASAP!

[solarbri]

Hello all,
I have two Yamaha T9.9XH2D outboards. They are set up for sea level and I will be running them at 7500 feet. What are the parts and part numbers that I need to help the things run right? Jets? Anything else? I'm hoping to go boating in 3 days, so I need to order this stuff and get it installed. ASAP!
Many thanks.
Brian

[solarbri]

Anyone?
Anyone?

...Bueler?

[solarbri]

Well, This is QUITE disappointing. Boats.net couldn't sell me the part that I need and suggested I come here and ask the question of which jet do I need before they can sell it to me. I wanted to order it on the spot. Here we are 3 days later and the "team of professional Yamaha mechanics" has let me down.

Are there high elevation (or altitude) jets available for this motor?



-Brian

[robert graham]

Since most of our lakes/rivers, etc. are at or near sea level(Upstate SC at 1000' above), maybe not so many experts here with experience operating at 7500' above sea level. My best guess is that your motor will run fine at 7500' above sea level, but with a bit less overall horsepower due to the thinner air. Maybe you should just run them as they are and see how they do. You could always go a size larger on the main jets, if you're gonna stay up at 7500'. Good Luck!

[solarbri]

Thanks Robert,

I am going on the trip anyway. I hope they run fine, we will see.
I kind of figured there would be a book or parts manual simply stating... "Yamaha T9.9H2D use standard jet for 0-3000ft., jet number-xzzx for 3000-6000ft., and jet number-yyyy for 6000ft. and up".

And it would definitely need to be a smaller size main jet. Not a larger one.
-Brian

[robert graham]

So with the standard carb/jet set-up, at 7500' your mixture would be slightly on the rich side, but these motors run so lean anyway, I doubt you'll see any difference at all, especially on a 9.9HP motor. Let us know how it works, and Good Luck!

[rodbolt17]

unfoutunatly there are no guidelines for high altitude gear ratios or jetting.
I have never tried running an outboat above about 500 ft above se*****l.
but yes thinner air will mean smaller jetting.
sometimes means a gear ratio and a prop pitch change.