Yamaha 9.9 to 15 hp

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joeyd

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Jul 4, 2005
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I have an older 92 Yamaha 9.9 hp 2 cycle outboard that I use on an Avon inflatable. Had it rebuilt 2 years ago but it just doesn't seem to have enough hp to move around with the the number of people that are usually at the boat. <br /><br />So I was wondering. There doesn't seem to be much difference between the 9.9 and 15 hp models. Is there some way I can upgrade the 9.9 to 15 hp? <br /><br />Joeyd
 
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rodbolt

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Re: Yamaha 9.9 to 15 hp

change the reed cage assy. thats about the only difference I could find. the power head assy and carb has the same part number. the reeds are different. i am doing my 9.9 as soon as the powerhead gets back.
 
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savasa

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Re: Yamaha 9.9 to 15 hp

Hi Joeyd!<br /><br />Please keep me and others updated:)<br /><br />To Rodbolt.. I have a 9.9D 1990 model can I only change reed cage assy to convert it to a 15hp or is my engine a different from the 1992 model!<br />Thanks!<br /><br />-G-
 
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joeyd

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Re: Yamaha 9.9 to 15 hp

Can it be that simple, just a reed assembly?? I thought it would be much more involved like a carb and powerhead. How did you manage to find out part #'s?<br /> <br />Thanks
 
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joeyd

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Re: Yamaha 9.9 to 15 hp

Rodbolt, what are you having done to the powerhead? I was also wondering if there are other things that can be done to increase power.
 
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rodbolt

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Re: Yamaha 9.9 to 15 hp

hello<br /> I am buying the powerhead assy new from yamaha. a dealer friend owes me a favor so its at cost. if its not still avalible I will be buying the crank and rod assy with new pistons. <br /> http://www.yamaha-motor.com/outboard/parts/home.aspx <br /> this is a link to an online parts catalog. ya go to the proper 9.9/15 section and see what is different. the parts smart is better but this site is most times ok. but about all I find different is the reed box assy.
 
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joeyd

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Re: Yamaha 9.9 to 15 hp

I think you were right on the money rodbolt. The only differences I see are the reeds and metering in the carburetor. This is more then I hoped for, should be a good boost in power.
 
L

likwidsukr

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Re: Yamaha 9.9 to 15 hp

joeyd said:
I think you were right on the money rodbolt. The only differences I see are the reeds and metering in the carburetor. This is more then I hoped for, should be a good boost in power.
Click to expand...
On the top end it will.
 
deejaycee_2000

deejaycee_2000

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Re: Yamaha 9.9 to 15 hp

I think the fuel pump is different as well ..... why not put a nice 30hp yummy on that avon inflatable? ....
 
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PurkaAamo

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Re: Yamaha 9.9 to 15 hp

You have to grind the carb to 19,5 mm, (15 mm on 9.9)
Main Jet to 135, move the reedstoppers from about 1.5 mm to 6 mm, newer reeds only 2 reeds and difficult to change to 3 reeds, if you want more power cantact the # 1 tuning guy HERRA RAANA, he has tuned well over 20 hp. from theese engines

yammu99.JPG


http://www.peramoottoripurkaamo.fi/
 
M

MOTION LINE

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Oct 9, 2004
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Re: Yamaha 9.9 to 15 hp

I have a feeling you need more carbs, one is not enough to give POWER at least 2 carbs is needed

Doubblecarb.JPG
 
M

MOTION LINE

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Oct 9, 2004
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Re: Yamaha 9.9 to 15 hp

FYI, it is not permitted to tune your engine if you intend to attend
the worldfamous KITÖ- LOPPET, only stock engines allowed,
remember no tampering or you will be DSQ!
:love:
0RMpjRsV_kito1.jpg
 
G

geo0001

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May 26, 2007
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Re: Yamaha 9.9 to 15 hp

Hi gents,

I own a Yamaha 9.5A (No. 650 S 26947) without knowing the precise year of manufacture. I've heard that the upgrade to 15 HP shouldn't be a big effort...

Is it the same construction as the 9.9 version, that had been discussed above? :confused:

What can I do?

I'd very much appreciate your help :redface:

So long
George
 
T

tcreps18

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Apr 21, 2010
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Re: Yamaha 9.9 to 15 hp

i have a suzuki 9.9 its a 1984 and am looking to convert it to a 15 hp also. would that be the same as jsut the reed assembly too? do you know?
 
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Paul.v

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Jun 18, 2009
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Re: Yamaha 9.9 to 15 hp

Old topic but no follow up if anyone has completed a conversion on Yamaha....I have 2 friends with 9.9 yamaha's that do circles around the 15 mercs....I can only assume they had been converted before they got the motors...I picked up a 9.9 (1989) now & wouldnt mind hearing from someone who knows....?
Thanks,
Paul

Does Iboats sell the plate & main jet? I cant find it if they do?
 
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E

Erkdajerk

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May 1, 2011
Messages
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Re: Yamaha 9.9 to 15 hp

To anyone considering the conversion from 9.9 to 15, I can confirm that the difference is the carburetor and the reed valve assembly. A side by side comparison of the parts in my hands confirms the following:

The 9.9 reed valve assembly has a total of 4 reeds and a blank space where the other 2 reeds would be. The 15 HP reed valve assembly has 6 reeds and uses all of the "available space".

As previously stated, the throat of the carburetor is noticeably larger for the 15 HP.

Of course, all of the above allows more air and fuel into the engine, thus creating more power.

Don't forget that producing more power won't do much good unless you also change the prop to take advantage of it.

I bought a solas 11pitch prop and that should do the trick.

I have completed the conversion on my 1987 9.9 but I have not had the chance to try it out yet. I can't wait.
 
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Foxtrot Unifom

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May 13, 2011
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Re: Yamaha 9.9 to 15 hp

I have a 2008 Yamaha 9.9 that I am about to convert to a 15 and according to the yamaha parts site the only difference is the reed valve assembly. the Carbs and reeds all have the same parts numbers...
 
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