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Thread: C Mod Secrets

  1. #11
    Team Member BRIAN HENDRICK's Avatar
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    Quote Originally Posted by Mark75H View Post
    You might as well just run the Stock motor. C Stocks often win in C Mod ... with the stock porting, the pipes seem to be decorations.
    The only advantage is that you may run a short tower ... which will help with handling
    Agreed, but the biggest advantage the mod motor has over the stock, is it can run as high as u wish w/o any cooling issues. Most stocks can't run above a 1/2" below w/o steaming. So if one wanted to run both stock and mod, and many do in C, then just switch lower units, change prop to a 4 blade, and jack it up an inch or so. I 'll bet there is 5mph right there

    PS; Ron, do u have any 4 blade 6 & 1/2" castings?
    Last edited by BRIAN HENDRICK; 09-02-2008 at 01:50 PM. Reason: sp?

  2. #12
    CANADIAN PRAIRIES REGION John (Taylor) Gabrowski's Avatar
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    Default Some Mercury 30Hs with expansion chambers can be exceptional

    For years there were Mercury 30Hs prowling races courses and national events that had expansion chamber exhausts and some other exhausts and modifications that worked well and won or placed in events handily. Problem with them though is their increasing antiquity, parts availability scarcity. Those who know how to really prepare them like Harry Brinkman and others wouldn't necessarily share their knowlege for posterity and competitiveness sakes with all those that would like to run like them too. They got them running over 8,000 rpm where many thought that not possible. No one can blame them for not sharing engine development secrets as they also provided services at cost to other racers to do so they too could do the same thing on race courses in terms of being front runners. The strange thing about expansion chambers and 30Hs is that they can work on 30Hs but that same exhaust technology does not easily adapt to bigger Merc 4s either. Merc's 30H engines will always be head scratchers.

    That is what its all about in racing. You either learn to do it or pay to do it and there is a lot of both always present out there in the face of declining parts sources making some people very inventive at times.

  3. #13
    Team Member Silas_53A's Avatar
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    A local C mod hydro racer said they once put a mod lower unit on a stock yamato with the lower water pickup and just a 3 blade prop I believe, and without much fiddling around they saw 4-5 mph increase.

  4. #14
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    Default C-Mod

    We ran C-mod for years in AOF and NBRA and tried just about everything there was to try on a Yamato C-Mod, we even turned one sideways and ran two pipes on it. We never could get a two pipe motor to work. The keys to being fast with C-mod Yamato whether it is a 102, 202, 302 is getting the pipe setup right. There are huge differences in pipes on these motors. At one NBRA race this year a guy came to test his C-mod and had 6 pipes and 6different props to find the best setup. He found it and is very fast!!! The best NBRA C-mods are all 202's which were not legal in APBA except pro. I have had all three engines and with an expansion chamber the 202 is best. We now run a 102 mod in NBRA C-runabout class with open pipe and geared 12/16 lower unit and haven't lost a heat in three years. When you are allowed to run any gear ratio it makes a big difference with an open pipe.

  5. #15
    Team Member Silas_53A's Avatar
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    I know the 202 isnt legal in c stock APBA buts its legal in pro? such as OSY400? But arent legal in mod classes? hmm...

  6. #16
    Sam Cullis Mark75H's Avatar
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    Quote Originally Posted by Silas_53A View Post
    I know the 202 isnt legal in c stock APBA buts its legal in pro? such as OSY400? But arent legal in mod classes? hmm...
    Correct, the 202 is a legal 400cc pro OSY400 motor
    Since 1925, about 150 different racing outboards have been made.


  7. #17
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    Thumbs up C Mod gearcase

    Quote Originally Posted by Ron Hill View Post
    Thanks, Sam. Seems those Yamato gearcases with the low water pick ups, and giant skegs, caught my attention....I just thought they were way cool, because they did start with a stock Yamato gearcase...


    So, if I had a 302 to run say C Runabut in stock and also ran C Mod....any problems with my C Mod, I could just take the powerhead of my C Stock and I'd be good to go????

    OK...With the bounce pipes which is better a 302 or 102??? Or does the pipe level the field???

    C Mod pictured with modified gearcase...
    Who transformed that gearcase? Do you have any more pictures of it?

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