Carb high speed orifice #'s

ruddy mudder

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Was looking up carb parts for my 1981 115 Johnson and noticed that the same year 90 hp has a larger high speed orifice number than the 115. Wouldn't the larger hp have a larger orifice number? The 115 is a size 60C and the 90 hp has a 65C while the 140 hp has a 67C. Isn't the higher the number the greater the fuel flow? Why the larger orifice number on the lesser hp?
 

racerone

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Is the carburetor venturi bore the same on the 90 and 115 HP model ?----Is the air flow and pressure the same in these 2 different motors and carburetors ?
 
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ruddy mudder

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Is the carburetor venturi bore the same on the 90 and 115 HP model ?----Is the air flow and pressure the same in these 2 different motors and carburetors ?
Different part numbers for all three Part #'s so I'd have to say no. Increasing the hi speed orifice from a lower # to a slightly higher # will it produce more on the top end? Just throwing out some ideas to get a little more punch.
 

racerone

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The 90 HP block has smaller intake ports in the side of the cylinder.
 

ruddy mudder

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The 90 HP block has smaller intake ports in the side of the cylinder.
If the ports are smaller, than why the larger orifice? The 115 must have larger ports but a smaller orifice? If a 90 orifice is installed in the 115 carbs, than the output of the 115 should be greater. 90 has a hole size of 63 and the 115 is a 60. Just trying to figure out what would happen if I increase the hole size in the 115 to a 63 or 65? The larger the hole, more fuel, why the smaller # orifice in a larger hp engine?
 

racerone

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Only one way to find.-----Book an appointment / time on a marine dynamometer at your local boat shop.-----Compare power output between the jets.
 

Faztbullet

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There are differences in carbs and block porting between a 90 and 115. The 115 carbs depending on model have bigger venturi,different emulsion and pull over tubes thus a different A/F ratio from carb.
 
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