converting 9.9 to 15

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Clancie
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2011/04/28 09:52:28 (permalink)

converting 9.9 to 15

Is it possible to convert a 87 mariner,9.9 to a 15. Carb. change? Is it worth doing as far as increasing speed on a 14 ft v bottom boat?
#1

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    bulldog1
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    RE: converting 9.9 to 15 2011/04/28 10:20:37 (permalink)
    Not sure it would be all that much of an increase, but.... I believe you'll have to change carburetor and exhaust tube not sure if there's anything else. It may be worth it and may not, but a lot of guys used to do it...
    post edited by bulldog1 - 2011/04/28 10:21:07
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    Erie Mako
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    RE: converting 9.9 to 15 2011/04/28 14:16:34 (permalink)
    It's not always as simple as "swap the carb"!
     
    Although many 9.9 and 15 horse engines may use the same engine block casting, some of the older Mariner/Merc blocks had larger intake ports for the "larger" horsepower engines, also like Bulldog said the exhaust tube might be different.
     
    There might also be a difference in the reed cage inside the block.
     
    If you find an inexpensive 15 horse carb. and it will bolt on...try it, you might have lucked out!
     

    On the internet, EVERYONE is entitled to their opinion!
    #3
    anzomcik
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    RE: converting 9.9 to 15 2011/04/28 15:15:33 (permalink)
    From what i have seen, if you want more power buy a motor with more power. I have a 14 foot semi vee that came with a 9.9 merc, no matter what i did it would do 8-9mph. I tried everything to make it plane out. Long story short, went out and got a 25hp mariner, two men loaded down heavy i do 23mph all day. My best every was very light load just me i got 28mph, but that was a one time only occurance in over 4 years.

    IMO you would be better off saving you time and money and buy a good higher hp motor. Also i am not sure if 15hp would be enough to plane you out (based off my boat, your boat might plane with the 9.9, i dont know the setup and every boat is different)
    #4
    spg
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    RE: converting 9.9 to 15 2011/04/28 16:28:53 (permalink)
    ORIGINAL: anzomcik

    From what i have seen, if you want more power buy a motor with more power. I have a 14 foot semi vee that came with a 9.9 merc, no matter what i did it would do 8-9mph. I tried everything to make it plane out. Long story short, went out and got a 25hp mariner, two men loaded down heavy i do 23mph all day. My best every was very light load just me i got 28mph, but that was a one time only occurance in over 4 years.

    IMO you would be better off saving you time and money and buy a good higher hp motor. Also i am not sure if 15hp would be enough to plane you out (based off my boat, your boat might plane with the 9.9, i dont know the setup and every boat is different)

     
    I have he same set-up except the 9.9 was changed to a 15.  Can get around 13 mph by myself according to the gps.  Had a 25 Merc on it and it was scary fast.  Clocked it at 37mph and still had more throttle.
    #5
    treesparrow
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    RE: converting 9.9 to 15 2011/04/28 20:44:23 (permalink)
    That 87 mariner should be a Yamaha as yamaha I beleave built the 9.9-15hp mariners at that time. I have a great 15hp
    Yamaha engine of that era that I would consider selling. It is just the complete powerhead with all electrics and carb,
    it is an elecric start and pull start. I have been looking for a blown motor to buy and put this one on.
    #6
    Clancie
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    RE: converting 9.9 to 15 2011/04/28 21:02:47 (permalink)
    appreciate the reply's. May be better to bite the bullet & get a 18 or 20.
    Thanks again.
    #7
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