Need advice on getting more speed
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Need advice on getting more speed

  1. #1
    Bouncing off rocks TryMe's Avatar
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    Default Need advice on getting more speed

    I have a 15' aluminum hull w/ delta pad bottom. Running a dominator pump, droop, inducer, ride plate, diverter, set back pump, and sbc. Turns a C impellor 5400, about 5900 on nitrous. GPS top speed w 2 people, fully loaded fuel,beer etc is 70 mph on nitrous.

    I have to run a standard rock grate, i run in a real shallow river, 6" - 8' at the deepest normally. Ive tried diffrent ride plate degrees that picked up 1 or 2 mph, but made the boat real loose and not want to turn like i need it to for running the river. I'm running a 2 7/8" nozzle, which seems to give the best performance. Im going through the engine this winter ,

    -forged pistons about 10:1
    -edelbrock rpm heads, 2.02,1.60, roller rockers
    -xm276 roller cam
    -weiand tunnelram w holley 450's
    -Rewarder OT headers 1 5/8" primaries
    -Full MSD igntion, locked out MSD dizzy

    Looking for 450-500 before nitrous



    The boat seems to ride low in the rear when on plane, but cavitates easily in anything more than 6" chop. I know i need a loader, but thats not really possible. Is it possible to get into the 80's with this configuration? Anything else i can try as far as setup?
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    Last edited by TryMe; 11-08-2008 at 03:54 PM.

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  3. #2
    Senior Member CK7684's Avatar
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    How big is the engine? I would try stroking it to a 383 if thats an option, then try a larger impeller...

  4. #3
    mo balls than $cents$ IMPATIENT 1's Avatar
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    put a single turbo blow thru set-up on it and it'd crank out 600+ with the same longblock

    Dare to be different, if it turns out great you can claim you planned it that way.

    Jetboatperformance.com

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  6. #4
    Bouncing off rocks TryMe's Avatar
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    its a 350. I killed my budget with the heads,cam, oil pan, intake setup etc already. I wanted to stroke it, just cant afford it. I'm hoping to be able to turn an A or A/B around 5000 without nitrous. I'm just wondering about making my setup more efficient, as thats a hell of a lot cheaper than buying horsepower

  7. #5
    Resident Ford Nut Sleeper CP's Avatar
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    Quote Originally Posted by TryMe View Post
    its a 350. I killed my budget with the heads,cam, oil pan, intake setup etc already. I wanted to stroke it, just cant afford it. I'm hoping to be able to turn an A or A/B around 5000 without nitrous. I'm just wondering about making my setup more efficient, as thats a hell of a lot cheaper than buying horsepower
    That might be a tall order for the 350". To make 500 hp with a 350 that's 1.41 hp /cu. in. It can be done but it's a very tall order to do it at 5,000 rpms.

    I built a 418" Ford for my dad. It made 500 at 5,000 and 525 Hp at 5,600 with a TR and 450's. That's 1.26 hp/cu in. I think you're going to either increase the stroke of the engine to get the 450-500 at 5,000 or your going to have to rev it much higher.

    Sleeper CP

    "Dark Sarcasm"
    Going fast is only half the fun ... what you make go
    fast is the other half.
    " A Government big enough to give you everything you want is big enough to take away everything you have"

  8. #6
    Large Member edog's Avatar
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    I run a SBC with an A @ 4200 rpm. It's all stock. Not sure if this any help to you or not.
    Last edited by edog; 11-07-2008 at 09:54 PM.

  9. #7
    Senior Member GT Jets's Avatar
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    If I may be so bold...All the horsepower in the world will do you no good if it won't stay hooked up, if it cavitates now, there is something wrong with your setup, I would suggest an inducer on the pump to help, and check the amount of rise or fall from the pad to the intake cup (may need to be shoed if way off), only then would I say more HP is in order.

    We have an aluminum 18' hull with a 377 SBC and run an AB impeller (ss) with an inducer at 5800 RPM and it will run 75 MPH with three people a cooler and a full tank of fuel......It can be done without a loader and with a heavy duty rockgrate.

    GOT pics? Aluminum is the new fiberglass

    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......

  10. #8
    Senior Member GT Jets's Avatar
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    Quote Originally Posted by edog View Post
    I run a SBC with an @ 4200 rpm. It's all stock. Not sure if this any help to you or not.

    IMHO you need to free up some RPM, small blocks like a little more revs, you have not even tapped into peak torque until 4,600 RPM.

    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......

  11. #9
    Bouncing off rocks TryMe's Avatar
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    GT - The only time it cavitates is in chop, on smooth water it hooks just fine. i have a flat bottom delta pad, not a radius. I have a DPS inducer installed as said earlier, helped a ton coming out of the hole. Like I said, it runs 70 now with a stock goodwrench crate motor.

    Im looking for advice on hardware setup, not hp. Is there anything i can do to my rock grate to load it better, but not jam more rocks in it when i run shallow? What can I do to lift the transom higher out of the water?
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  12. #10
    Senior Member GT Jets's Avatar
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    Quote Originally Posted by TryMe View Post
    GT - The only time it cavitates is in chop, on smooth water it hooks just fine. i have a flat bottom delta pad, not a radius. I have a DPS inducer installed as said earlier, helped a ton coming out of the hole. Like I said, it runs 70 now with a stock goodwrench crate motor.

    Im looking for advice on hardware setup, not hp. Is there anything i can do to my rock grate to load it better, but not jam more rocks in it when i run shallow? What can I do to lift the transom higher out of the water?
    15' boat = a little dangerous at ultra high speed, that being said....I think you are in need of a droop, this will lower the thrust angle of the propulsion and increase transom lift while enhancing the overall handling. The reason for the ass heavy attitude IMO is due to the boat being short (read; "bow light" boat) the factory style rock grates do offer pretty good protection (finger type), but you can get away with a plate type too, the openings are actually smaller than a finger grate and much stronger, that would be the direction I would go, we have run these for several years and yet to have a rock related failure due to the loader. Let me know your thoughts...

    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......

  13. #11
    Large Member edog's Avatar
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    Quote Originally Posted by GT Jets View Post
    IMHO you need to free up some RPM, small blocks like a little more revs, you have not even tapped into peak torque until 4,600 RPM.

    GT
    I meant to say A impeller. Oh well. 4600 would
    be nice, but my boat is all stock. I was trying to throw out a base line number. not too many people on the boards run small blocks.
    Last edited by edog; 11-07-2008 at 10:00 PM.

  14. #12
    Senior Member GT Jets's Avatar
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    Quote Originally Posted by edog View Post
    I meant to say A impeller. Oh well. 4600 would
    be nice, but that would mean HP.
    If your getting 4200 RPM with a baby Chevy, thats a good running motor, I would put "B" cut in that rig and see what happens....Just my opinion and not my $$$$$$$$.

    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......

  15. #13
    Sit N' Spin Jetaholic's Avatar
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    No replacement for displacement. Run a big block.

    Just my $0.02



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  16. #14
    Senior Member GT Jets's Avatar
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    Quote Originally Posted by Jetaholic View Post
    No replacement for displacement. Run a big block.

    Just my $0.02

    A big block in a 15 foot boat is like a blower for your Tercel Unless of course that big block is made aluminum

    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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