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Thread: Fast Fred's Secrets of the OMC MOD50's Thread #1

  1. #411
    Team Member Bill Gohr's Avatar
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    Quote Originally Posted by John Taylor
    Back to the OMCs, to make them cooler other than ditching thermostats if present what other cooling tricks can be used to specifically cool them down and keep them that way? Any old Deflector Alky Merc tricks of any use?
    As far as cooling on the 56 cu in blocks, we had many variations to the cooling system on those engines, if you look at the bridge port engines you'll see we changed it at least 6 times between 86' and 93', and after we came out with the 94' oval port engine the cooling system was corrected as well as the piston fit was tightened up.

    If you have a bridgeport engine, look at where the water by passes at the bottom and on some of them you can plug that all up and get some more direct flow, some you'll see an angle drilled hole up the bottom headed toward the exhaust side of #2 that was to cure a hot spot next to 2, if you plug that you'll stick it, if you have that block. You'll see other ones with 1/8" pipe plugs to plug some cross drilling we tried, some helped, non corrected the issue til 94'.

    When I was at OMC I baby sat this thing through all these changes.
    Last edited by Mark75H; 11-25-2008 at 08:28 PM.

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    good stuff, can you tell us more on the coolin system of the 56er.

    testin is key,

    i'll check out that Konig stuff.

    i talked to a Dude that worked at OMC, he built Mod50 31m Modas and dynoed them. he said that he used a 56 case, a 31m front 1/2, long rods, trick pistons,
    and down exhaust and put it on the dyno and made a pull.

    got more, i gots to go now, go and test motors, it's cool kinda fun.

  3. #413
    Team Member Bill Gohr's Avatar
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    Quote Originally Posted by Fast Fred View Post
    good stuff, can you tell us more on the coolin system of the 56er.

    testin is key,

    i'll check out that Konig stuff.

    i talked to a Dude that worked at OMC, he built Mod50 31m Modas and dynoed them. he said that he used a 56 case, a 31m front 1/2, long rods, trick pistons,
    and down exhaust and put it on the dyno and made a pull.
    Yes we did run 56's with 2 bbls on them, and there were lots of people puttin Merc rods and pistons in them.

    I wrote a book on the cooling mods for the in house people back in "93

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    Team Member Sam La Banco's Avatar
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    Bill, were any of the 56 cuber 2 barrel motors you are talking about able to run strong without the staggered bore 2 barrel set up or extensive mods to the stock exhaust manifold system?

    I never saw to many of them, but the ones I saw all had problems dealing with the stock 2 barrels and all the fuel they could deliver. They just did not seem to get up and go, as strong as expected, even with the additional cubes. Not even close to a mod 50. Even with a Mod 50 crank case and reeds.

    The 56 cuber manifolds inter-cylinder tunning length in its stock configuration are not suited with or without the SST 60 pipe.

    You've seen a lot more of them then I did, just wondering.

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    Team Member Bill Gohr's Avatar
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    Sam thats always been the issue, the exhaust. I've seen alot of guys do some real nice work on the inside of engines, porting, shaping, even 3 3/8" bores and longer rods, and what are we gonna do with the exhaust, nothing. So most of that stuff never ran worth a damn. You're stuck with the inside casting of the exhaust, and ya need the 60 tuner assy.

    When I built the prototype personal watercraft engine, Macier made a exhaust manifold that was 60 dimension but turned 90 degrees, and I made the engine lay on it's face and put super BN's on the side, now that motor would accelerate with those pumpers on it, I had 38's on it to do our boat testing, I was gonna grind on it and go with 42's but marketing pulled the plug on the OMC "Shockwave" personal watercraft. I never had the time to figure out if it was the carbs that acted so well or the fact that when I shortened the front of the engine, all the way to the crank, and put the carbs on the side, was it the smaller crankcase?

    And you are right, the best carbs were the staggered bores, I think that little motor just didn't have the signal it needed. Well we know it didn't, thats why those carbs worked.............

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    Team Member Sam La Banco's Avatar
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    Thanks Bill,

    If I can figure out how to do it, I will post some pictures of an intake manifold I designed for the 3 cyl. OMC engines. It was designed to adapt large single barrel pumper carbs of up to 1.770" bore diameter to the stock intake manifold. I did this for all the same reasons you just talked about. I had some casting of it made and machined. When I was going to build an sst70 motor. I thought I would have better luck with large single barrel pumpers than the dual barrel set up.

    Then the power head just sat there for years all tricked out with finger ports and the whole ball game. I even machined out the cast in manifold, and made a new one. I finally sold the thing Whittingtons in Canada. I don't think they ever ran it.

    Maybe someone would be interested in one of the manifolds if they would want to try the same thing.
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    Team Member Bill Gohr's Avatar
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    Yep those pumpers were like fuel injection, you just look at it and it was running, I don't think I put a primer on it, you could just start it and grab a handful, nobody in house liked to see Mikuni's on our engine.

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    Team Member Sam La Banco's Avatar
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    There is a great story about when they could not start the rotary motors and the Mikuni guy was there. But thats a story for an other day.

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    Team Member Detroit Whitey's Avatar
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    I`m in the middle of doing just What you guys are talking about.I gave the two barrels a try and that was a wash so i`ve been playing with all types of carb & intake set up`s. Had to much of a problem getting it to start on a off the dock start i ended up going back to the sst60 carbs.Well it works but i know like all of you know there`s more so i`m back to the drawing board. Liked the the cooling talk also. GOT A QUESTION why are the guys running the 49ers in the mod classes running the water backward from stock? Sam your adapter looks great but what would you do for the reeds?
    Last edited by Detroit Whitey; 12-01-2008 at 07:23 PM. Reason: forgot somthing

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    just food for thought and i didnt read all the reply's but all you talking about bigger carbs????... i own the kilo in class ..and i used the 55hp carbs????...go fig,,,maybe just set up?? or lots luck????...

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