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Thread: Porpusing

  1. #1
    76SLEEKCRAFT STREAKER dave flynn's Avatar
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    Porpusing

    Thankyou for response. Do you have a good source for trim tabs to help eliminate the porpusing ? And angles. I am tool and die from back ( When within a thou is close enough LOL) New to Jet boat world and hooked for sure. I want to have this old girl run down lake sporting the best roost she can as flat as she can. Rick from CP walked me through the Berkeley rebuild and was very patient LOL. Do you think try trim tabs and ride plate? Like I said not worried about top end speed just flat and nice roost. I will leave top end up to my girl (Plenty there LOL) Thanks so muchClick image for larger version. 

Name:	roost.JPG 
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Size:	268.4 KB 
ID:	19498 That pic it was porpussing like crazy My girl thought she was going to come out of the boat (and not in a good way) Thanks again. PLEASE HELP

  2. #2

    Re: Porpusing

    I would talk with cp again, explain your symptoms and vids are always helpful. Like a before and after way to document the progress. They should be able to set you with a long enough ride plate. Tabs would work. But way overkill and 3X the cost and headache to install. An adjustable ride plate will make all the difference in the world. How much of a droop did you go? 4"??? Dean
    AG6= Amazing Grace VI *
    1980 BIESEMEYER 27' VIKING

  3. #3

    Re: Porpusing

    Quote Originally Posted by dave flynn View Post
    Thankyou for response. Do you have a good source for trim tabs to help eliminate the porpusing ? And angles. I am tool and die from back ( When within a thou is close enough LOL) New to Jet boat world and hooked for sure. I want to have this old girl run down lake sporting the best roost she can as flat as she can. Rick from CP walked me through the Berkeley rebuild and was very patient LOL. Do you think try trim tabs and ride plate? Like I said not worried about top end speed just flat and nice roost. I will leave top end up to my girl (Plenty there LOL) Thanks so muchClick image for larger version. 

Name:	roost.JPG 
Views:	28 
Size:	268.4 KB 
ID:	19498 That pic it was porpussing like crazy My girl thought she was going to come out of the boat (and not in a good way) Thanks again. PLEASE HELP

    If it has a droop you may wanna try it without. Is it better or worse with less tail/roost? Alot of times porpoising is from not havin enough hp to carry the nose.
    Another thing that can do it is over charging the intake....but if you dont have a loader or shoe I doubt thats your problem.

  4. The following user Likes H20MOFO's post:

    AG6

  5. #4

    Re: Porpusing

    Hi Dave,
    Porpoising is a very simple thing to understand. It is caused when the hull of the boat is at the Apex, and trying to 'climb out of the hole' or over the crest of the wave of water its on, if you will. Another words, the boat is at a teetering point(like a see-saw) and the balanced is being upset. Not enough drag to hold down the nose, when you lift the bow(bring the nozzle up) so it starts to teeter up and down. One excellent way to correct this, is the use of a "Ride Plate" under the bowl of your pump. This in effect tricks the hull in to thinking its longer than it is, and creates enough surface drag (or parasitic drag) to actually compensate for this bouncing. Most of the Jet boat guys use these for this reason, and you'll notice that you may also pick up a few MPH and better handling as well. CP, PJB and many of the aftermarket boat part house carry these, but I'd recommend you take the boat with you and some current video of how its reacting. This will give these folks the info they are going to ask for, to help you select a ride plate. Almost all boats have this issue. I/O's (like my Biesemeyer) has it too, I just use trim tabs to correct it. Good luck, Hope this all helped. Dean.


    Last edited by AG6; 06-28-2017 at 05:59 PM. Reason: Merged post.
    AG6= Amazing Grace VI *
    1980 BIESEMEYER 27' VIKING

  6. #5

    Re: Porpusing

    It may be as easy as losing the droop....and wont cost ya anything. Not all boats respond well to lowering the thrust line. Just my .00000002

  7. #6

    Re: Porpusing

    [QUOTE=dave flynn;106552]Thankyou for response. Do you have a good source for trim tabs to help eliminate the porpusing ? And angles. I am tool and die from back ( When within a thou is close enough LOL) New to Jet boat world and hooked for sure. I want to have this old girl run down lake sporting the best roost she can as flat as she can. Rick from CP walked me through the Berkeley rebuild and was very patient LOL. Do you think try trim tabs and ride plate? Like I said not worried about top end speed just flat and nice roost. I will leave top end up to my girl (Plenty there LOL) Click image for larger version. 

Name:	roost.JPG 
Views:	28 
Size:	268.4 KB 
ID:	19498

    Hey Dave, made any progress on the trim issues you were having or ride plate install?
    AG6= Amazing Grace VI *
    1980 BIESEMEYER 27' VIKING

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