Has anyone experimented with light or heavy flywheels in Jet boats?
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Has anyone experimented with light or heavy flywheels in Jet boats?

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    Senior Member Daddy B's Avatar
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    Question Has anyone experimented with light or heavy flywheels in Jet boats?

    I have a 50 lb flywheel, a 35 lb flywheel, and a aluminum fly. The motor is a healthy 427 bbc 11.5 comp., going in this 21 fairly light cruiser. Just curious if there would be any noticable differences. I thought the 50 might give me a little more torque but I really don't know. Any experience out there.........I got a feeling someone has tried it......Thanks ahead of time.
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    Senior Member GT Jets's Avatar
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    Quote Originally Posted by Daddy B View Post
    I have a 50 lb flywheel, a 35 lb flywheel, and a aluminum fly. The motor is a healthy 427 bbc 11.5 comp., going in this 21 fairly light cruiser. Just curious if there would be any noticable differences. I thought the 50 might give me a little more torque but I really don't know. Any experience out there.........I got a feeling someone has tried it......Thanks ahead of time.
    All depends on what you're going to do with the boat...

    I like light flywheels (aluminum) because of the rate of decel (play on rivers and good throttle response is required).

    A heavy flywheel can help prevent overreving the engine when you vent the pump, but otherwise don't know of any more positives one way or another....

    GT
    GT


    Quote Originally Posted by Quickjet View Post
    Put a 300 on the back of it, Flywheel it and a nosecone. $15,000 later you'll have a 65 mph pile of shit......

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    Senior Member DuaneHTP's Avatar
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    Go with the light flywheel. The pump shaft and impeller are already acting as a flywheel. Why add more weight to the boat?

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    Senior Member EVILFORCE's Avatar
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    Use a flex-plate for a automatic trans. Lighter yet.
    No Fool Like A Old Fool is there?

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    Boat Nut sleekcrafter's Avatar
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    X 3 use a good flex plate (SFI) also employ a rev limiter...
    Upper Midwest Power Boat Association
    DRAG BOAT RACING UMPBA #926


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    Senior Member jetboatperformance's Avatar
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    Quote Originally Posted by sleekcrafter View Post
    X 3 use a good flex plate (SFI) also employ a rev limiter...
    Keyword "good quality" you havent lived till you've thrown a counter weight

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    NW Spectraholic Malcolm's Avatar
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    I've tried both ways with my mild Oldsmobiles. Maybe a tad bit quicker accel, hard to tell. I thought I'd really feel a big difference, but no.
    Malcolm

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    Senior Member OUTLAW HALLETT's Avatar
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    Quote Originally Posted by jetboatperformance View Post
    Keyword "good quality" you havent lived till you've thrown a counter weight
    that 427 shouldnt have a counter weight,,,should it ?

  11. #9
    Senior Member Daddy B's Avatar
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    Well, That's easier, I have a good quality flex plate on it, and the whole motor is perfectly balanced so maybe I'll just leave it on there.....I wasn't sure if I could run a flex plate only. I wondered if a heavy flywheel would give it more rotating mass and give me higher rpm's and slightly higher mph. The motor is coming out of the v drive. I am going to change to a different cam, with lower rpm range.

    Thanks for the feedback.

    I still don't know what impeller is on the thing.... might be a or aa. Is there a easy way to tell what size of impeller?

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    Senior Member Schiada 201's Avatar
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    I ran a flex plate back in the 60ts accelerates faster and when off the peddle stops quicker. It came in handy when running against a first timer in the turns and anywhere else.

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