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Thread: yamaha 70 ces

  1. #11
    FFX-61
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    Part one of "Secrets of the OMC Mod 50" : http://www.boatracingfacts.com/forums/showthread.php?t=2052

  2. #12
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    it's ok, more to read...
    I dont' want to start tuning the engine, just determine of the engine has mods or not...
    And keep the engine safe, it's not for racing. just pleasure...
    I'dont know the history of the boat and engine...
    The guy i bought it from, bought a big warehouse that was gone bankrupt.
    The boat was in the deal...
    Sat 8years in storage before i bought it...
    Placed a new battery, cleaned the fuel thank, replaced the worn fuel lines and primerbulb.
    Checked the carbs but they where drained,good thing! Impeller was in good condition.
    I thought that in the picture engine is completly trimmed in, I can give it more neg trim if needed...
    Yes, water pick up is in the bullet.
    A guy who i spoke to said it was a barracuda to, indeed no cell.
    Hope the prop will run fine. If not, mod it...

  3. #13
    FFX-61
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    the nose cone pickup will push the core plugs out of the head. should have a 000 serial number on the case. 17deg advance is good on the stock ces head. you should weld the crank. 90hp carbs make it go, 160 main jet

    Part one of "Secrets of the OMC Mod 50" : http://www.boatracingfacts.com/forums/showthread.php?t=2052

  4. #14
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    oh, the tuna, it's chrome plated steal, they rot off fast, best to have it copied in stainless is nice, alu' works

    Part one of "Secrets of the OMC Mod 50" : http://www.boatracingfacts.com/forums/showthread.php?t=2052

  5. #15
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    so i better check each time the core plugs, is there a way to secure them better?
    Only drived the boat once with to small prop, i think i had then about 15psi water pressure...
    Is the crank that bad? and what do you need to weld?
    Will take a look at the tuner when i take the block of the shaft.
    When searching for info over the yamaha ces, found alot of your posts fred...
    Seems you have alot of experience with this motors...
    Why should it have that serial nb on the case?
    To fit the the 90hp carbs on the 70hp engine, i assume you make the holes off the reed plate bigger?
    no Further suprises when mounting the carbs?

    Its difficult sometimes with these technical terms

  6. #16
    Team Member 88workcar's Avatar
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    I think you will be quite happy with this rig just the way it is. I wonder how it ever made it sence all this stuff is wrong or going to break as soon as you try to use it. I am baffled.If you ever need 90 carbs which I don't think you do, I have about 30 sets, just let me know.
    Helping folks out around the globe.

  7. #17
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    Default I did get some e-mails from other racers about the 70 CES.

    I thought I would post rather than e-mail several people and go back and forth.

    I can only relate to my experience with the motor and how we would inspect any motor racing in T class in Ontario Canada.

    First there were two UIM inspection sheets numbers 398 and 435 [I think there the numbers].
    There are two different blocks. You can tell the later block because it has the mounting blocks for the newer style ignition. The one in this thread is the older block.
    The original motor does not have 90 hp carbs. It has the older style 60 and 70 hp small carbs.
    The crank, rods and pistons weight 1000 grams
    Based on the original Specs from Japan the motor is 70 hp at 6400 RPM.
    The compression is 150 psi.
    The horsepower curve drops quickly after 6500 rpm. The motor will turn 8000 with very light load. The igniton is a weak link to run the motor a very high rpm over long periods of time.
    The bell shaped short tuner helps to get higher rpm on a tunnel, but the stock tuner has more torgue and is equal or better on a V bottom.

    The designers in Japan copied the OMC Stinger. The gear case is 1.71 ratio on the CES and 1.76 in the OMC. They both are 15 inch mids, off centre chamber heads, The horsepower curve is raised from 70 hp at 5500 to 70 in the yamaha at 6400 and 75 plus at 6000 in the OMC. Based in prop shaft HP the OMC is a little stronger. The big reason is the weight of the rotating assembly The yamaha is very heavy.
    You pin or weld the crank on a CES or any modular crank in a performance application because they shift out of phrase. That changes the timing.

    Racers in Europe motors pass inspection. That is their inspection and their business.
    In T Class here we decided on a maximum compression rule of 160 psi. The motors are stock and run on pump gas, not super stock. Inspection is first fault, easiest first. Visual is first, next is compression. If it reads over 160 psi your out.

    Can this motor run over 100 mph in the kilo on a F4 tunnel? Not in my opinion unless it was on a trailer pulled behind a car.

  8. #18
    Team Member ima75man's Avatar
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    Default stock moters

    if racers spent more time on props and setup, they would be faster than most racers modifying their moters.
    out front again

  9. #19
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    Well, it did in at least once in 1992 - 101.93MPH - UIM record. Since the motor is no longer legal in European/World class races like Rouen, there's probably good deals to be made.

    Quote Originally Posted by Hounddog View Post
    Can this motor run over 100 mph in the kilo on a F4 tunnel? Not in my opinion unless it was on a trailer pulled behind a car.
    Argo Cat 18 - Sold
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  10. #20
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    Quote Originally Posted by FrenchPhil View Post
    Well, it did in at least once in 1992 - 101.93MPH - UIM record. Since the motor is no longer legal in European/World class races like Rouen, there's probably good deals to be made.
    Yes Sir, it's in the book and thats a 2 way average. Doing the math he turning a 26 pitch prop at over 8000 RPM from a 70 hp motor.

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