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Mercury 99 4stroke

J

John Lindstrom

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Why is my Mercury rated at 9.

Why is my Mercury rated at 9.9 HP when a 15 HP has the same bore and stroke? Where do they get the extra power?
 
" John,

There are a number


" John,

There are a number of ways to change the horsepower. Different exhaust tube, carb bore diameter, different high speed orifice, just to name a few.

Generally the engine is designed for the higher horsepower, and then they reduce the horsepower in different ways so they can have two or three different horsepower configurations from the same engine.

This makes marketing more efficient.

Tony "
 
Is there any way I can find o

Is there any way I can find out how to bump it up to 15 HP? It's a 1999 Mercury 9.9 EXLH four stroke.
 
" John,

It appears that the


" John,

It appears that the only difference on that engine is in the carb. You would have to replace the main jet and horn, but I am still looking for any other differences in the carb.

Tony "
 
"John,

I think you would ha


"John,

I think you would have to replace the entire carb, but it is difficult to tell for sure from the pictures, and I do not have two carbs that I can examine at this time.

The parts manual shows different carb part numbers for the two engines, which leads me to believe that there is some basic difference in the carb body itself, possibly a different bore diameter.

The carb is the only thing that I can find that is different between the 9.9 and the 15.

There are two different gearcase ratios, but it seems that they used both on either engine.

Tony"
 
Thanks for taking the time to

Thanks for taking the time to help me.
 
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