How to make my 9.9 a 15?

[Bretz56]

I have a 2004 johnson 9.9 four stroke that I need more power out of. Can anyone tell me if I just need a carb off a 15hp or is there more that needs done? Thanks in advance

 

[Tim Frank]

Re: How to make my 9.9 a 15?

The archives have a lot of threads with this type of question.
"I bought a X HP. but I want a X+5 HP (or whatever)."

The general consensus is that it is a can of worms....don't open it.
Sell the 9.9 and buy a 15.

I have not yet seen a thread where someone came back and said anything like "I redid my 6 HP. and now it is an 8 HP. and runs great".

 

[boobie]

Re: How to make my 9.9 a 15?

Agree + 1 with the above. Buy a bigger mtr.

 

[Bretz56]

Re: How to make my 9.9 a 15?

Guess I will try a 4 blade prop first! Mainly just looking for more low end power

 

[Tim Frank]

Re: How to make my 9.9 a 15?

You might want to swing into the Prop forum and get a few opinions in there before trying to adjust performance on a 9.9HP by re-propping.....unless you can borrow the 4-blade.

 

[gozierdt]

Re: How to make my 9.9 a 15?

With the older two-strokes, changing the carb was 90% (a rough estimate) of the difference
between 9.9 and 15 hp engines (the smaller changes were a modified exhaust pipe, and
spacers under the reed valves). I doubt it's as simple with the 4-strokes, so I agree, you
can try a different prop for a small difference, or a bigger engine for a larger difference.