carb swap 15 to 20 ?

[gfd434]

i have 1986 johnson 15 hp , will a 20 hp carb fit it ? im needing just alittle more hp thanks

 

[jimmbo]

Re: carb swap 15 to 20 ?

no

 

[Dhadley]

Re: carb swap 15 to 20 ?

Will it fit? Yes. (How good a machinist are you?) Is it a direct bolt on? No, far from it. Will it add 5 hp just putting on a carb? No.

 

[gfd434]

Re: carb swap 15 to 20 ?

Will it fit? Yes. (How good a machinist are you?) Is it a direct bolt on? No, far from it. Will it add 5 hp just putting on a carb? No.
i'm not a machinist,but i have a friend that is. what are my options and what will i gain by doing it ? thanks

 

[steelespike]

Re: carb swap 15 to 20 ?

You will gain next to nothing the the 15 is 13 cu. in.
the 20 is 31 cu in.Its pretty obvious the the 15 is allready pretty much at its max.It's possible a 20 hp carb will make it slower and more difficult to operate.

 

[Dhadley]

Re: carb swap 15 to 20 ?

With stock port timing you're only gonna get so much fuel / air in. And out. You could build an adaptor but the stock hood and pans aren't going to work any more.

Were you planning to do porting also?