4ST main jet replaced with 6hp jet. Won’t reach full rpm

[WyattPile1996]

I recently replaced the 4hp main jet in the carburetor with the 6hp size main jet. The motor fired up and idled fine, as expected, but when throttled up it bogs and won’t reach full rpm. Do I need to make an adjustment on the carburetor or do I need to replace the main nozzle too?
I used to get 14-18kph and now maximum of 10kph.

 

[boscoe]

I suspect too much gasoline. Motor will be down on power.
Reinstall the correct jet.

 

[faztbullet]

Tis more than a jet change to make it a 6hp

 

[Edchris177]

Getting more power is not as simple as throwing more fuel into the motor. The ratio of fuel/air has to be maintained. Your 4hp carb cannot move more air, but you are adding fuel, resulting in an over rich condition, as Post #2 stated. Lots of people have triEd making a 9.9 into a 15 by only installing a larger jet, resulting in your symptoms.
if you need more power, buy a bigger motor.