Changing Carb Jets on 1991 90 horse

[mtblackdog]

First I need to know how to figure out which jet Im running, and if it is the original sea level jets, and if they are I want to go one jet smaller or leaner. Is this something I should tackle or better left to a true wrench turner. I am running at 3000-5000 ft in elevation and need to get motor up to WOT. I have already raised the motor and am taking the next step before I have to go down in pitch on my prop. Currently on level plane at full throttle I am running 5200 RPMs and 38 MPH with a 13 1/4 X 17 pitch prop. thanks in advance

 

[ob]

Re: Changing Carb Jets on 1991 90 horse

If you'll look close on the jets ,there may be a orifice number stamped on them.Otherwise an indexed set of tip cleaners and a 0-1" outside micrometer will do the trick.Your engines original orifices should be idle orifice 38C and high speed orifice 56C.

 

[mtblackdog]

Re: Changing Carb Jets on 1991 90 horse

OB-What is the procedure for changing them out?

 

[ob]

Re: Changing Carb Jets on 1991 90 horse

They unscrew .To access the high speed jets you'll need to first remove the screw plugs that cover them.You'll need the proper size screwdriver blade with shank that will not interfere with the threaded hole as they will round off easily if stuck.

 

[mtblackdog]

Re: Changing Carb Jets on 1991 90 horse

Thanks ob Ill take a look at them tomorrow.

 

[mtblackdog]

Re: Changing Carb Jets on 1991 90 horse

ob-what is the part number for the next leaner carb jets.

 

[Dhadley]

Re: Changing Carb Jets on 1991 90 horse

All jet sizes are listed in the manual by size and then part number. Do not - do not - use "D" jets in your motor. Stick with "C" jets. They look the same but are very different.