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Tohatsu 9.8HP conversion to 15HP?

D

doxmit

New member
Hi,

I have a 2003 Tohatsu M9.8B 2 stroke engine, short shaft, and I wish to convert it to a 15HP engine. I am aware some folks have had success with other models by simply changing the carburetor. Is it that simple with this model? Can anyone help me with this?

Upon further reading I have found a throttle advance cam change will solve my challenge - is that correct?
Here is the part link: http://www.internetoutboards.com/partdetail.asp?id=505

</start invitation for user abuse>And for the non-engineer - what does a throttle advance cam do? I get why the 15HP Carb would improve performance - but if I don't have to change the carb - then all the better. </end inviation for user abuse>

Finally, can anyone share perfomance improvement stories or a quick list of other engine checks I should be performing to max performance?

Many Thanks,
Doug
 
Last edited:
Sorry, no. You have a 9.8A, not a 9.9D2. Completely different animals. You cannot upgrade your horsepower.
The 9.9 is the "little sister" of the 15, and in some circumstances, can be upgraded to 15, by making the carb open all the way at WOT, which is what the throttle cam does.
Yours is the "big brother" of the M8B, and is already the most that frame size can do. It is already "upgraded".
 
Rats on the upgrade - I got the serial number yesterday - 2001, M9.8B SN:22379

Any suggestions on how to get 15HP out of a similar frame size?

Many Thanks,
Doug
 
Um, Nitrous oxide injection? Seriously, you have the max that you can have. If you need more, you will have to go with a bigger motor.
 
I to have a Tohatsu M9.8B 3K9 Outboard ser. No. 031220XK and I am wanting to up the HP to 15 Is this now possible since the previous person asked.?
 
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