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  1. Convert Mercury 25hp to a 30hp

    I just bought the 2007 Mercury 25hp outboard with batteryless EFI. How do you convert it to a Mercuy30hp. Where can I get a stainless steel prop for this new motor.

  2. #2
    Join Date
    Nov 2005
    Location
    Plaisance, Québec, Canada
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    482
    OK, up to my 02, i don't think that you could increase the HP to this extent BUT i've seen miracles happen every days ( laugh )

    As for the prop, i believe that your dealer could set you up OR the trade and Sale on this forum could be an option...
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  3. #3
    Join Date
    Apr 2001
    Location
    Windsor, Ontario
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    4,528
    One way would be to go through the parts manuals and see what's different. Same bore and stroke, so the short block is likely the same. Could be porting, valves, camshafts, all of the above.

  4. Quote Originally Posted by tscimemi View Post
    I just bought the 2007 Mercury 25hp outboard with batteryless EFI. How do you convert it to a Mercuy30hp. Where can I get a stainless steel prop for this new motor.
    If the long blocks are identical, then it can be done through the magic of software ! Swapping the ECU should do it, unless there are some magic "things" buried in the harness that say, "This is really a 25HP, so don't make any more power !"

    Aren't computers fun !

  5. #5
    My best advice: leave that motor alone.
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  6. #6
    Quote Originally Posted by tscimemi View Post
    I just bought the 2007 Mercury 25hp outboard with batteryless EFI. How do you convert it to a Mercuy30hp.
    A 5hp shot of the silly gas

  7. #7
    Join Date
    Aug 2001
    Location
    Annapolis, MD ragboat capital of the world
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    10,253
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    Quote Originally Posted by Scream And Fly View Post
    My best advice: leave that motor alone.
    Probably the best advice ... if you need a 30, sell the 25 and buy a 30

    2007 motor? Isn't it still under warranty? A change like that will completely void all of the warranty

    I think current EPA rules would require any shop to return it to all original configuration if they have to work on it (if anything breaks in the future).

  8. #8
    Join Date
    Oct 2007
    Location
    Sydney, Australia!
    Posts
    25
    The Two motors are the same. The only difference is a spacer infront of the carby which limits air flow. Go to a Mercury dealer and get it taken off and swapped for a 30hp spacer. I have had two of those motors and trust me 5hp makes a big difference.
    Does it void the warranty? im not sure.

  9. #9
    Join Date
    Nov 2002
    Location
    Lake Lanier - Atlanta, GA
    Posts
    110

    Doubt you can make it a 30hp...

    The 2007 25EFI Mercury (Tohatsu) is a digitally fuel injected 4-stroke and you would need to have the computer changed to make it a 30hp... The 30hp Mercury (Tohatsu) computer would cost you more than just selling your motor and buying a 30hp...

  10. #10
    port and polish the intake ports and throttle body. i gained 2mph by doing this. I plan on doing this to the head soon see if i can gain 2 more mph.

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