[Question] Please help. Having issues with porpoise at wot
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Please help. Having issues with porpoise at wot

  1. #1
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    Default Please help. Having issues with porpoise at wot

    Hi there everybody!

    I have a 18ft Nordic Bubble Deck Jet Boat. This boat porpoises like crazy at WOT.

    Here are the specs:
    496 BBC
    Berk Split Bowl, with a Berk Droop
    Place Diverter
    Back cut shoe (currently 1/8 below keel)/ride plate (currently 4 deg)
    SS loader

    I've been told to just use the Diverter. I've used it and I can get it to ride perfect at WOT but the Diverter is pretty far down.

    What can I do to make it better??? Less degree on the ride plate? More shoe??

    I only seen one Post from a guy who said he got his Nordic to run perfect but I can't seem to get a hold of him on here.

    Any and all help is greatly appreciated!!!!

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  3. #2
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    I have the same type of boat I believe.

    Mine only seems to want to porpoise at slower speeds with the diverter "too high"....I dont have any issues at WOT an can run the diverter as high as I want as long as im in the pedal.

    I do not have a loader, shoe or ride plate.

    I do have: dominator 12-S pump, american turbine diverter, american diverter droop.



    Have you checked for hook in the hull?

    Does your hull have the "spoon" bulge before the pump intake for the coanda effect? (Coanda Effect)
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    Last edited by SS496; 03-12-2018 at 10:42 AM.

  4. #3
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    Is your pump set back..or stock location?

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  6. #4
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    There is always cav plates!
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  7. #5
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    Quote Originally Posted by Gone Green View Post
    Is your pump set back..or stock location?
    Stock location. I'm wondering if I should wedge downward to straighten up the exit of the droop and nozzle. I have a 4 deg wedge just sitting at the house.


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    Quote Originally Posted by waterfun#1 View Post
    There is always cav plates!
    But isn't that the purpose of angling siren the ride plate, of one has one? I have one on my boat (ride plate).


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    Quote Originally Posted by SS496 View Post
    I have the same type of boat I believe.

    Mine only seems to want to porpoise at slower speeds with the diverter "too high"....I dont have any issues at WOT an can run the diverter as high as I want as long as im in the pedal.

    I do not have a loader, shoe or ride plate.

    I do have: dominator 12-S pump, american turbine diverter, american diverter droop.



    Have you checked for hook in the hull?

    Does your hull have the "spoon" bulge before the pump intake for the coanda effect? (Coanda Effect)
    Hi there. Sorry for the delay response. Life got in the way.

    I porpoise at around 3000RPM... I have to drop the Diverter down a notch from the best MPH position. When I get the boat up to 3300-3500 there's no porpoise at all.

    The conada effect is what gives an advantage to the Nordic in regards to hole shot right?

    I really think I need to wedge down the Berkeley droop. Correct me if I'm wrong but doesn't the Berk Droop have more of an angle coming out the exit than a PD (Place diverter) droop?


    Thank you for replying!


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  10. #8
    Senior Member ol guy's Avatar
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    Quote Originally Posted by lvilla03 View Post
    Hi there. Sorry for the delay response. Life got in the way.

    I porpoise at around 3000RPM... I have to drop the Diverter down a notch from the best MPH position. When I get the boat up to 3300-3500 there's no porpoise at all.

    The conada effect is what gives an advantage to the Nordic in regards to hole shot right?

    I really think I need to wedge down the Berkeley droop. Correct me if I'm wrong but doesn't the Berk Droop have more of an angle coming out the exit than a PD (Place diverter) droop?


    Thank you for replying!


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    Until you put a straight edge on the bottom of the boat you will spin your'e wheels making pump changes. If it has a hook in the back of the boat at the transom all the direction changes to the hardware will not change a thing. The set-up you have now should be fine but with a hook in the chines at the back of the boat it will constantly want to drive the bow down and the power and pump will want to lift the bow. The hook (not spoon) is the first point to start. Just to explain (if you don't know) no offense intended. The spoon is forward of the intake and the hook is at the bottom of the boat at the transom all the way across the beam. Normally 6-8 inches in, if so sand it down smooth across the whole back of the boat(don't worry they are laid up with alot of glass in that section of the hull) and the speed hop will be gone! M

  11. #9
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    Quote Originally Posted by ol guy View Post
    Until you put a straight edge on the bottom of the boat you will spin your'e wheels making pump changes. If it has a hook in the back of the boat at the transom all the direction changes to the hardware will not change a thing. The set-up you have now should be fine but with a hook in the chines at the back of the boat it will constantly want to drive the bow down and the power and pump will want to lift the bow. The hook (not spoon) is the first point to start. Just to explain (if you don't know) no offense intended. The spoon is forward of the intake and the hook is at the bottom of the boat at the transom all the way across the beam. Normally 6-8 inches in, if so sand it down smooth across the whole back of the boat(don't worry they are laid up with alot of glass in that section of the hull) and the speed hop will be gone! M
    No offense taken!!! I appreciate the help. So it would be easier to sand down the hook rather than fill? If I was to sand down do I need to add any type of speed coat to the sanded areas?

    Thank you again for your assistance!


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  12. #10
    Senior Member ol guy's Avatar
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    Quote Originally Posted by lvilla03 View Post
    No offense taken!!! I appreciate the help. So it would be easier to sand down the hook rather than fill? If I was to sand down do I need to add any type of speed coat to the sanded areas?

    Thank you again for your assistance!


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    To answer you're question about fill in the low, If you have access to a 6 foot straight edge and lay it down the bottom of the boat and see just how much you would need to fill rather than take (normally) 3/8 to 1/2 inch of material off the transom area. Again the lay-up in that area is more than thick enough to allow for the change, and as far as a coating---Yes cover the sanded area. Now I am going to give you the 1000.00 gift. Just go buy a can of high temp black(0r whatever color matches the boat) header paint. does the same job at 5 bucks a can. Let me know what happens. M

  13. #11
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    Quote Originally Posted by ol guy View Post
    To answer you're question about fill in the low, If you have access to a 6 foot straight edge and lay it down the bottom of the boat and see just how much you would need to fill rather than take (normally) 3/8 to 1/2 inch of material off the transom area. Again the lay-up in that area is more than thick enough to allow for the change, and as far as a coating---Yes cover the sanded area. Now I am going to give you the 1000.00 gift. Just go buy a can of high temp black(0r whatever color matches the boat) header paint. does the same job at 5 bucks a can. Let me know what happens. M
    Just an add-on alot of times you will need to either slide the boat back on the trailer or lift the stern to get access to the area that needs work,normally the chines need a clean-up too and the trailer bunks get in the way. Lift or slide--your'e call!!! M

  14. #12
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    Quote Originally Posted by ol guy View Post
    Just an add-on alot of times you will need to either slide the boat back on the trailer or lift the stern to get access to the area that needs work,normally the chines need a clean-up too and the trailer bunks get in the way. Lift or slide--your'e call!!! M
    Thank you sir! Greatly appreciated!


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  15. #13
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    Quote Originally Posted by lvilla03 View Post
    Thank you sir! Greatly appreciated!


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    Let me know how it works out for you!!! M

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