2008 9.9 2stroke conversion to 15hp

[flatsfisher26]

Hi, new here & I'm wondering if anyone has any experience with this..
I've been told that my 2008, 9.9 2stroke Yamaha can be converted to a 15 hp by simply changing out the reed valve assembly.
I've compared the part #'s for the 9.9 & 15hp & the only difference I see with the carb and intake diagrams is infact the reed valve assembly.

Is it really that simple?
Any info on this would be greatly appreciated.

[almetelo]

Hi!

A few months ago I've been searching on the web how to improve my F80a to F100a (carbs) and after read most I could find (a lot of wrong ideas and sarcatics comments) found the answer on the manual parts comparing the diferences of these 2 motors (on fuel injection models are few more diferences and much more expensive because need change ECU)
At the time when talked with my local Yamaha Marine mechanic he confirmed I could do it (they already did it many times before) Even when I asked the price parts for the F100a he already knew what I wanted hi!
Keep in mind that must be illegal but no one have to know hi!

My sugestion is:

Find a manual parts for you outboard and one for F15 +/- same age and check if they mach and what are the diferences.

What is your outboard code? I'll check if I can help you.

Good luck.

[almetelo]

Don't forget motors must share same engine block! I guess on lastest models F15 share the same engine block with F20

[rodbolt17]

biggest difference is the 15 uses a 3 reed intake and the 9.9 uses a two reed intake.
however its illegal to modify an EPA based motor.
EPA motors started in 1998.

[flatsfisher26]

Thanks for the replies everyone.
I had no idea there were legal ramifications to doing such a thing.
I'd still like to know if swapping out the reeds will give me another 5hp.

Almetalo: It's 9.9 MSH

[almetelo]

ok but need to know motor code.

You can find it close to the serial number

Something like this:

F9.9 (code) (S/N)

[flatsfisher26]

Ok. This it what I've got.

9.9 MSH
682k, S, (Then serial #)
H

[rodbolt17]

for US market motors manufactured after 2005 the model number indicates the basic model and the production date will be the determining factor in the seriel number run.
so occassionally I have to have all 3 numbers to correctly look up parts.
its funky but it is what it is.

[eliup007]

hey guys can you tell me if this lower unit will fit my engine?
the part number that I need its 60C-45300-11-4D but has the same part numbers and components as the 68V-45300-12-8D.
I want you to check it out and give me an opinion.
I'll put some attachments for you to see.
thank you!

[flatsfisher26]

Almetalo, Rodbolt17,
Did you guys find any differences according to part #'s with the 9.9 & 15 two stroke?
I haven't.

[almetelo]

Hi!

So far I didn't found what I'm looking for to help you

Soon I can If I can... I'll let you now!

But Rodbolt is a expert and FOR SURE he knows what is talking about!

So... must be just or mainly the reed valve.

Your model is a little old and make things a little dificult to help you.

[almetelo]

Hi again!

Find it...

I was looking for on wrong files! hi hi

682 is the code for older models (80's) I know you said 2008 but I thought could your purchase date.

682K is effectively the lastest models.

Right code 63V 682K

As said previously Rodbolt is right!

The only diference I found on motor was the reed valve.

Yours is part #63V-13610-00
for 15HP part is # 63W-13610-00

Have a look:

http://www.twineye2002.com/Products/...rts%20Book.pdf

If you go ahead with this mode let us know the results.

Good luck.

[almetelo]

By the way...

9.9FMH is the european/world version but exactely the same as 9.9MSH US/canada version depending on serial #
If you send me the serial # I can confirm it.

I'm almost completely sure that will do

[flatsfisher26]

Awesome!
Thanks almetalo!
I'll let you know how it turns out.

[flatsfisher26]

Well I went ahead and did it...
Swaped out the old 9.9 reed valve assembly with the new 15 hp reed asembly.
I'm very happy with the results! There is a definite increase in power. It's most notable in the mid to upper range.
I have this motor on a 14' Carolina Skiff. The motor used to struggle to get the boat on plane with 2 adults & now there is no problem at all. I guess 5hp makes a big difference with a little boat.

Thanks everyone for your help. Especially Almetelo!
I'll try to add a few pictures of the reed valves so you can see the difference.