Thread: Fast Fred's OMC Mod 50 secrets Thread #2

  1. #621
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    Default Mod-50 front ends

    Can't say for sure if SeaWay has any loose fronts - you might call Dave Losvar. But, I've got a one angle 8-petal, one straight 8-petal, and two 10-petal crankcases. Some have manifolds/reed plates and cages. Unless you're lucky, some mill work and align boring are needed to match an existing block. If you're looking for a matched set, I've got at least one angle 8-petal and one straight 10-petal block & crankcase available. Send a PM with your needs.

    Tim

  2. #622
    modifiedoutboard OUTBOARDER's Avatar
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    Quote Originally Posted by Tim Kurcz View Post
    Can't say for sure if SeaWay has any loose fronts - you might call Dave Losvar. But, I've got a one angle 8-petal, one straight 8-petal, and two 10-petal crankcases. Some have manifolds/reed plates and cages. Unless you're lucky, some mill work and align boring are needed to match an existing block. If you're looking for a matched set, I've got at least one angle 8-petal and one straight 10-petal block & crankcase available. Send a PM with your needs.

    Tim
    how much for an angled 8 petal front half only?
    ANTHONY McCULLOCH
    modifiedoutboard@hotmail.com

    Some things never change!

    They Want it cheap..............

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    Team Member fs5's Avatar
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    Quote Originally Posted by Tim Kurcz View Post
    After Rich Welch set the 850MH 3-mile 4-lap record with "Kestrel" in August, I decided to shift gears from class racing and build project "Virgo" just for me. It will be in the test tank mid-April. Will test the limits of the 45SS gearcase........

    Tim
    while this thread is sorta on the turbo topic.
    this may sound like a dumb question.
    but has anyone tried using a belt/gear driven blower to suck the exhaust gas out rather than force more air through the carbs?
    it seems most people raise the exhaust ports to get more gas out.so why not suck it out?
    its just a thought i've been thinking for a while now .

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    Sam Cullis Mark75H's Avatar
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    It would suck exhaust out, but it would end up lowering the pressure in the cylinder. Torque and resulting horsepower is increased by increasing cylinder pressure.

    Raising ports allows a motor to turn more rpm, the other possible way to increase horsepower. This is done at the expense of slightly lowering torque. If the rpm raises dramatically without the pressure falling equally dramatically, horsepower increases. If the pressure decreases too much, the motor runs more rpm without making more power - possibly making less power.
    Since 1925, about 150 different racing outboards have been made.


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    Default Pop off valve

    Quote Originally Posted by formeone View Post
    dont see a adjustable waste gate tim???... stories of old turbos... when let off throttle engine just kept going deff need pop off valve,,,...
    Hey Fred, I forgot to answer your question about the pop off valve:

    One of the benefits of a draw through system is a pop off valve is not needed. With the carb in front of the turbo, there is no fuel mixture available for combustion once the butterfly closes. The engine quickly consumes available plenum volume and slows quickly. Rapid throttle closures are hard on the turbo thrust bearings due high vacuum in the compressor side; but at least the vacuum draws lube oil past the bearings into the inlet system - causing a brief puff of exhaust smoke.

    In a blow-through system with butterflies downstream of the compressor the issue is instant plenum over-pressurization upon rapid throttle closure which can cause great damage to the turbo thrust bearings because much greater force can be applied by pressure than vacuum. This is the real reason for the pop off valve. Also, the high pressure spike can exceed lube oil pressure creating starvation of the runaway 150,000 RPM+ turbine shaft/bearings which leads to premature bearing failure.

    There's definitely alot to this turbo project - over 80 hours of research and engineering not including the build so far. I'm just hoping it doesn't grenade on the first pass!

    Tim

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    speed its an obsesion clough's Avatar
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    tim fit that turbo powerhead under a regular cowl they'll never see you comin lol

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    Default No sleeper

    Unfortunately, it won't fit under a cowl, and also needs free air cooling. It will be in the open for all to see - including the marine patrol unfortunately!

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    Quote Originally Posted by Tim Kurcz View Post
    Unfortunately, it won't fit under a cowl, and also needs free air cooling. It will be in the open for all to see - including the marine patrol unfortunately!
    Eww water nazis

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    Default 2011 race season

    OK boys, this thread has been quiet for too long, so time to cause some mayhem........ The 850ccH class will get livelier this summer. K3 is about to be unleashed!
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    Default 2011 play season

    Just in case you think engine building is all work and no play......... The mockup is complete; it's time to assemble the real thing.
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    Last edited by Tim Kurcz; 05-16-2011 at 06:32 PM. Reason: Anecdotal comment

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