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Thread: Tween 55 and WOT boat porpoises badly

  1. #1
    For whatever reason, I can't keep the boat on a smooth ride ~55mph +. Have all the goodies: droop, ride plate, hyd div., speed coat. There is also a narly wedge ~10-12 degrees, not sure what size but pinkish FTN. Could it be the nozzle or wedge? The motor and pump have both been moved back 4.25". I am hoping that this isn't this reason. Mainly, I am looking for a starting point to tweak rather than something so big.
    Also, in relation to the smooth water topic post: many of you said you weren't as fast on glass, but are you a smooth ride on glass?

  2. #2
    Hey, i have very similar problem with my 75 sanger super jet. it porpoises bad around 3-4k rpm. i have a wedge and a droop with a small ride plate. i was trying to take the wedge out because i got alot of feedback that, that was probably alot of my problem. but when i get on it full tilt it smooths out just fine. i just couldnt get the droop to seperate from the wedge. so im stuck now. havent got any info on glass water yet, just this boat last week.

  3. #3
    Senior Member
    Join Date
    Feb 2009
    WOW...thats a whole bunch of wedge!...most people i read or hear about are only running 4* of suggestion is...take the wedge out & try it with the ride plate angle & diverter angle...there is a sweet spot that the diverter likes...nothing to lose by trying these suggestions... but a little time

  4. #4
    Ken F
    It's impossible to correct your problem through the forum, however the cause of it is that your boat is rocking back onto the ride plate, and then back onto the hull. (porposing) If you think about what is happening in this window, you should be able to come up with a solution(s)
    You should be able to change the thrust angle with your divirter, so I would doubt that your wedge is affecting you. Your boat is going to run it's fastest with about a 3' rooster. There is where you want to tune your set-up to.
    With the divirter handle in about mid position, you should have about a 3'er.
    Sounds like a lot of wedge. In order to get your rooster at about 3', you have to be bending the water twice. (once upwards with the wedge, and back downward with the divirter)
    My guess would be that you may have hook in the back of your hull, causing the bow to be pushed back down as it trys to rock back on the rideplate, or your ride plate is adjusted too high.
    Hope this helps
    Ken F

  5. #5
    Senior Member
    Join Date
    Apr 2010
    Managed to solve a few with a degree or two down on the rideplate.
    I can make mine porpoise with too much angle. I've done it several times over the years when tuning for max speed. Drop the plate down a little at a time just enough to settle it (no porpoise).
    Could be other contributing factors like Ken said, but this one's a cheap fix and only takes a little time and some gas.
    I likes cheap fixes!

  6. #6
    i agree with squirtcha....had the same problem in a biesemyer jet between 3 and 4000 rpm it about threw me out of the boat.....about a half inch down on a good ride plate and it rode as smooth as glass. good luck

  7. #7
    Thanks for all the help. Will start to weed some of these things out a bit. Will let you know what works for future reference. 10 to 12 might be a bit much, but the wedge with the diverter throws a 40' high 150-200' roost.

  8. #8
    Don't worry about the wedge, lower your ride plate a little at a time and you'll fix it. Good luck

  9. #9
    not to sound like a complete idiot, but in which direction am i lowering the angle? At the rear end of the plate, or at the front of the plate. With fasteners at rear of boat and then between the pump and plate, it looks as thought adjustment should be easy, but which point am i adjusting?. Having trouble envisioning the physics of what change will do what.
    or am i just lowering it overall...both spots?

  10. #10
    Adjust rideplate at very back of boat, were it bolts to your bowl.

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