Flywheel VS Flexplate
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Flywheel VS Flexplate

  1. #1
    AKA OhOneWS6 Last Mohican's Avatar
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    Default Flywheel VS Flexplate

    I tried to search on this and didn't find any real discussion on it. I know of 3 that failed in the last 6 months. I know two of those were flywheels. I am not sure on the third. What is your choice and why? It might also be good to include how you use your boat and what your HP & torque numbers are.
    Last edited by Last Mohican; 01-24-2013 at 07:26 PM.

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    SFI approved flexplate here, 800hp lake boat.

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    Senior Member jetboatperformance's Avatar
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    Quote Originally Posted by bbfsouthwind View Post
    SFI approved flexplate here, 800hp lake boat.
    X's 2

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    Senior Member rpm0414's Avatar
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    JW stuff is one of the best I came across

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    Default Failures....

    The majority of the flywheel/flexplate failures I've seen were related to starters and ring gears... I have personally "flexed" an aluminum flywheel so quickly the ring gear fell off, twice.... I've seen several chewed up ring gears from those small "high torque" aftermarket starters, 4 on Allerton's PS52 boat alone..... I currently use an aluminum flywheel from Bergeron, bought from Brockhouser at LB in 08, and it's worked great with 13.1:1 and a bone stock GM high torque starter mounted Powerglide style to the bellhousing with 39* locked out in the mag...... I've used flexplates, GM, or Jeg's, in several recreational jet boats for decades, also with stock GM starters. In 40 years I've never had to shim a Chevy block mount starter, Pontiac yes, Chevy no......Another area to think about is the battery. You NEED a good HOT battery to crank anything without busting something.... If the motor CAN kick back, it will...
    Ray
    LOUD BOATS SAVE LIVES

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    Try to use the best you can buy . I have seen a sfi flex plate peel the ring off ,kinda rare but it happened. last weekend a buddy of mine had a flywheel explode tore a hole in the bottom and side of a pc tunnel and it sank . once upon a time ihad an external balance bbc weight come off the flywheel and lucky enough went thru the bell housing without damaging anything else . What scares me if it can tear up that much stuff on the boat imagine what it could do to the boat you running along side

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    AKA OhOneWS6 Last Mohican's Avatar
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    Quote Originally Posted by Moneypit View Post
    The majority of the flywheel/flexplate failures I've seen were related to starters and ring gears... I have personally "flexed" an aluminum flywheel so quickly the ring gear fell off, twice.... I've seen several chewed up ring gears from those small "high torque" aftermarket starters, 4 on Allerton's PS52 boat alone..... I currently use an aluminum flywheel from Bergeron, bought from Brockhouser at LB in 08, and it's worked great with 13.1:1 and a bone stock GM high torque starter mounted Powerglide style to the bellhousing with 39* locked out in the mag...... I've used flexplates, GM, or Jeg's, in several recreational jet boats for decades, also with stock GM starters. In 40 years I've never had to shim a Chevy block mount starter, Pontiac yes, Chevy no......Another area to think about is the battery.
    Quote Originally Posted by Moneypit View Post
    You NEED a good HOT battery to crank anything without busting something.... If the motor CAN kick back, it will...
    Ray
    Thanks for the input Ray. So far you are the only one to post that is using a flywheel. Is there a reason why? I understand it is a nice piece and not a stock GM flywheel. The failures I have seen are catastrophic. I believe all three were stock flywheels. All that is left is a couple of very small pieces at the crank flange. These were way more than just a ring gear failure. I totally agree on the hot battery. Not sure why your reply is divided into 2 quotes. I tried to fix it but it keeps changing back.

    Quote Originally Posted by bradyte083 View Post
    Try to use the best you can buy . I have seen a sfi flex plate peel the ring off ,kinda rare but it happened. last weekend a buddy of mine had a flywheel explode tore a hole in the bottom and side of a pc tunnel and it sank . once upon a time ihad an external balance bbc weight come off the flywheel and lucky enough went thru the bell housing without damaging anything else . What scares me if it can tear up that much stuff on the boat imagine what it could do to the boat you running along side
    Was this at the Winter Nats in south TX? That is the one that I was unsure if it was a flywheel or flexplate. the 3 failures I know of have been very lucky that no one was hurt.

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    Senior Member kdub's Avatar
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    Quote Originally Posted by Last Mohican View Post
    Was this at the Winter nats in Houston? That is the one that I was unsure if it was a flywheel or flexplate.
    It was an sfi aluminum flywheel. There is not one spec of it left to be found anywhere in the boat, just a piece of the ring gear. There is a gap between the pto and crank with all bolts like it was never there! Check your installations guys and make sure you have done all you can do to prevent a failure! Parts still fail when everything is right, but this type of damage not only cost a lot of money, but could get you hurt or someone next to you.

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    "BOATLESS" blender over's Avatar
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    After i saw what can happen like "Dominator" on the forums, his flywheel exploded at the track and left some nasty scars on the transom, lucky it was not sawed in half
    I bought this SFI approved billet one off of Jegs or summit, i think it was like $300-$400 but the piece of mind is worth it with high HP applications.
    I have a deep cycle battery ive had sense i bought the boat, high torque starter and 950+hp on the nitrous, i dont want shit to break laying down a pass at the river.
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    Senior Member kdub's Avatar
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    nice piece blender!!

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    i run a flexplate on my blown alky in a jet, my family ran flywheels in their PE and TE hydros

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    "BEER BUDGET RACING" Bodean's Hammer's Avatar
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    SFI flexplate with the good heavy cast aluminum flywheel cover, not the thin stamped unit.

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    "BOATLESS" blender over's Avatar
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    Quote Originally Posted by kdub View Post
    nice piece blender!!
    Thanks the new setup has been a loooong time coming..
    Looking foward to a good upcoming river season.

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    Senior Member 76 Bonneville's Avatar
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    No problems so far. Running a Meziere billit steel flex plate and a Meziere starter to match.

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