9.9 Johnson to 15 hp with Carb jets?

[kalloway]

Someone mentioned that I could increase the hp in my 1978 Johnson from 9.9 to 15 hp by just changing the carburetor jets. Is this correct? Does anyone have any experience doing this?

 

[Bear]

Re: 9.9 Johnson to 15 hp with Carb jets?

No, you have to get the bigger carb from 15 hp. Check with your dealer.

 

[kalloway]

Re: 9.9 Johnson to 15 hp with Carb jets?

Thanks for the reply. I'll be visiting a dealer soon, waiting on some parts I ordered for a 1962 3hp. Before I go, do you know if anything other than the Carb is changed, gaskets etc? Someone had mentioned that they thought the leaf valves were different? Have you seen one run that was changed?

 

[Dhadley]

Re: 9.9 Johnson to 15 hp with Carb jets?

The cylinder head is different also but unless you are turning 6000 RPM or more you wont see much of an improvement. And then it depends on the hull design of your boat. The reeds are the same. If you are over 6 grand you might consider Boyesen reeds.