convert 2004 yamaha four stroke 9.9 hp to 15hp?

[cmarsh33]

hey i have been trying to find out the FACTS about converting a 2004 yamaha 9.9 four stroke to a 15 hp. I have heard several things such as carb change, reeds, exhaust. If any outboard mechanics have info on this topic i would be greatly appreciate finding out if it is possible on a 2004 four stroke.

 

[Mackerel King]

Re: convert 2004 yamaha four stroke 9.9 hp to 15hp?

I have a similar (2005) 9.9 and am wondering the same thing. Searching through the archives I see a lot of talk of 2 strokes or general statements about why or why not you should try this but no definitive answers as to what parts are required for the 4.

 

[Mackerel King]

Re: convert 2004 yamaha four stroke 9.9 hp to 15hp?

Anything different other than the carb on this year?

 

[Mackerel King]

Re: convert 2004 yamaha four stroke 9.9 hp to 15hp?

This 9.9 is yearning to be a 15. He just needs a wee bit of help...

 

[Silvertip]

Re: convert 2004 yamaha four stroke 9.9 hp to 15hp?

No reeds on a four stroke. That's what the valves are for.

 

[Mackerel King]

Re: convert 2004 yamaha four stroke 9.9 hp to 15hp?

I am aware of that and not the OP. When I look at the parts diagram I see no difference other than the carb. Anyone out there know if there are any other differences for 2005 9.9 4 stroke.

 

[VTJ]

Re: convert 2004 yamaha four stroke 9.9 hp to 15hp?

I was a Yamaha service manager and the only difference on most yamaha's was the carb had a stopper on it so the throttle couldnt open fully...I have a 9.9 Johnson 4 stroke and there is no stopper on the carb and it looks to be opening fully so I am not sure..would like to find the answer also