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  1. #1
    Cadet
    Join Date
    Mar 2012
    Posts
    2

    Default Tohatsu 9.8HP 4 Stroke to 15 HP Upgrade Not Quite Right?

    I've been reading the forums on this topic but still have a couple questions. I have 2010 tohatsu MFS9.8A3EFS model and am interested in the HP increase modification I've read about. I've read that simply need to replace carburator to 15 HP model and that's all. But when I look at Tohatsu website the specifications for the 9.8 and 15 HP are quite different.

    For example:
    9.8 HP
    -209 cc displacement
    -82 lbs

    15 HP
    -351 cc displacement
    -114 lbs

    I don't understand how the 9.8 can develop the 15HP with 140 fewer cc displacement? Also the weight difference is a concern. The 15 HP carb isn't going to weigh an extra 30 lbs, so that means that there are addtional differences like shafts, gears and other components that would need to be bulked up on the 15 HP model? It just doesn't add up. Thanks in advance for all the information on the forums, it is a great resource!

  2. #2
    Petty Officer 2nd Class
    Join Date
    Mar 2010
    Location
    Caribou, ME
    Posts
    151

    Default Re: Tohatsu 9.8HP 4 Stroke to 15 HP Upgrade Not Quite Right?

    From my understanding you cannot make the 9.8 into a 15, you are talking about two completely different engines whether two or four stroke. I think people are seeing 9.9 and 9.8 and thinking they are the same engine, they are not.

  3. #3
    Captain pvanv's Avatar
    Join Date
    Apr 2008
    Location
    Western NYS
    Posts
    3,920

    Default Re: Tohatsu 9.8HP 4 Stroke to 15 HP Upgrade Not Quite Right?

    Correct. Some (not all) 9.9's could be upgraded. The 9.8 is not a 9.9; It is already the "big brother" of the 8 hp motor; i. e. it has already been "upgraded".
    Paul
    Certified TLDI Technician
    Buffalo NY USA

  4. #4
    Cadet
    Join Date
    Mar 2012
    Posts
    2

    Default Re: Tohatsu 9.8HP 4 Stroke to 15 HP Upgrade Not Quite Right?

    Ah, very good. 9.9 vs 9.8, i'd never have thought they were different. good thing we have such knowledgeable people on the forum with lots of experience. thanks for saving me the carb swap!!

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