How possible is it to gain 7.1-8 mph if I simply...
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How possible is it to gain 7.1-8 mph if I simply...

  1. #1
    Senior Member PonyFiveO's Avatar
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    Default How possible is it to gain 7.1-8 mph if I simply...

    I helped my little brother pick up his first jet boat this past Saturday and took it out on it's maiden voyage (under it's new owner) on Sunday at Modesto Reservoir.

    The boat is a nice little 79' Nordic Bubble Deck with what seems to be a stock 454, Air Gap intake and HEI, vacume secondary Holley (750?), stock Dominator pump, and over transom logs. With me driving (245 lbs or so) and 15 gallons of gas, it went the best of 62.9 MPH in choppy conditions, which we are pretty happy with considering the reasonable price we paid.

    Without going into the motor, I am fairly positive that we could gain the 7.1-8 MPH (hopefully on the conservative side) we are looking for in search of 70 MPH with just the following...
    • Loader
    • Droop
    • 2 or 4 degree wedge
    • Bassett or Rewarder Headers
    • Place Diverter (or not)
    Hopefully we can find all the parts we need used to stay in my little brother's budget

    What do you experienced folks think? Possible?





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    Last edited by PonyFiveO; 08-23-2010 at 09:37 PM.

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  3. #2
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    It is kinda hard to guess things like the weight of the hull, how much hook is in the bottom of the boat etc. etc. I can tell you that my 700 lb rogers with a small hook in the bottom went 69mph with a 396 when I bought it. It had the pump in the stock location with a droop, place diverter, blueprinted pump and a crapy loader grate...... I dont think that it would be too hard.

    Good Luck

    Chris

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    Senior Member moneysucker's Avatar
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    I would put diverter at the top of the list then loader, droop, headers. I am sure you will see some gain with headers but you need to get it to the water efficiently. I would suggest a 6-9" blocker loader to get a little lift in the rear since there is no Ride plate. You lose a little on the holeshot but will see it on the top end.

    Cy
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    Resident Ford Nut Sleeper CP's Avatar
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    Quote Originally Posted by moneysucker View Post
    I would put diverter at the top of the list then loader, droop, headers. I am sure you will see some gain with headers but you need to get it to the water efficiently. I would suggest a 6-9" blocker loader to get a little lift in the rear since there is no Ride plate. You lose a little on the holeshot but will see it on the top end.

    Cy
    You forgot 850 DP carb and trim the impeller to get a few 100 more r's out of it.

    He didn't say what it's reving now. Hey what's it reving ?

    Where's Quickjet his boat ran in the 80's with 450 hp.

    S CP

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    Senior Member PonyFiveO's Avatar
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    Quote Originally Posted by Sleeper CP View Post
    You forgot 850 DP carb and trim the impeller to get a few 100 more r's out of it.

    He didn't say what it's reving now. Hey what's it reving ?

    Where's Quickjet his boat ran in the 80's with 450 hp.

    S CP
    Actually, I do not know what rpm it was at. I think the Beede tach may be wired incorrectly as it only read a max of 3000 rpm. It sounded like mid 4000 rpms though.

    Any idea how to set this tach right?

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    check the back of the tach and make sure that it set to 8cylinder setting.
    that might be the cause.

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    Senior Member harley222's Avatar
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    nice boat i have its twin lol..
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    i'm back!! 1QuickCP's Avatar
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    yup...1st if ya have one of those crappy little flame arrestors inside the airscoop...lose it.
    2nd good accurate tach
    Blueprint pump and check/cut impeller,check bottom for hook
    loader, diverter,droop,wedge, 850 holley

    I'd leave headers for last if at all..

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    "BOATLESS" blender over's Avatar
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    Quote Originally Posted by 1QuickCP View Post
    yup...1st if ya have one of those crappy little flame arrestors inside the airscoop...lose it.
    2nd good accurate tach
    Blueprint pump and check/cut impeller,check bottom for hook
    loader, diverter,droop,wedge, 850 holley

    I'd leave headers for last if at all..
    How bad does the little flame arrestors restrict?
    I have one but dont know what to replace it with considering my scoop is very short.

  12. #10
    i'm back!! 1QuickCP's Avatar
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    Those things are Horrible !! Put on on a flow bench once years ago and lost like 20% air flow if I remember correctly.. even the large all stainless $$$ one's need to be gutted as well...

    Look at it this way, the "screens" they sell to go between the blower and the carb spacer are like 1/8" open mesh..they cut air flow 5-7 % over a open hole.

  13. #11
    "BOATLESS" blender over's Avatar
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    Quote Originally Posted by 1QuickCP View Post
    Those things are Horrible !! Put on on a flow bench once years ago and lost like 20% air flow if I remember correctly.. even the large all stainless $$$ one's need to be gutted as well...

    Look at it this way, the "screens" they sell to go between the blower and the carb spacer are like 1/8" open mesh..they cut air flow 5-7 % over a open hole.
    Soo what do i replace it with?
    Here is my scoop, not alot of options.
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    Quote Originally Posted by blender over View Post
    Soo what do i replace it with?
    Here is my scoop, not alot of options.

    K&N air filer with no oil.

    S CP

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  15. #13
    I'm No Expert Shaun's Avatar
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    PD
    Droop
    Loader

    That would be my order.

  16. #14
    i'm back!! 1QuickCP's Avatar
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    Quote Originally Posted by blender over View Post
    Soo what do i replace it with?
    Here is my scoop, not alot of options.

    Yup the good ol k&n ....i'd just remove it and make a holdown bracket for the scoop...or try flippin the scoop backwards with nothing, that is legal most everywhere I think...those small dooley scoops look bitchin but the flame arrestor is a huge problem in them.. I ran them backwards on my hallett.
    One thing you can do that I have done is get some 1/8 aluminum screen and cut it to fit in the scoop front a bit back from the opening, then get someone who REALLY knows how to use a tig and spot weld a few little blocks of aluminium in the scoop to screw the screen to.. I actually made a tiny "frame" for the screen out of billet plate, it volted to 3 little blocks with 10-32 bolts.


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