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  1. #1
    Member
    Join Date
    Mar 2010
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    Bailey, NC
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    80

    HELP WITH PORPOISING

    I have a 2008 ZX 200 with a HPDI 200 that required a replacement of my 12" jackplate due to one of the ears breaking. Had the same model Slidemaster manual jackplate installed and now the boat porpoises bad on midrange rpms.

    PTP was at 4.0", moved to 3.50" and had issues getting on plane. Moved to 3.75" and comes out of the hole better but still porpoises at 3500-4500 rpm's.

    I had Croxton B&B the prop (25 Temptest Plus) and tried my spare 4 blade Fury 24 with the same result.

    Any ideas as the porpoise issue was not as much a problem before the jackplate replacement.

    Thanks,

    Skeeterman70

  2. Member
    Join Date
    Sep 2015
    Location
    sand springs, ok
    Posts
    185
    #2
    Didn't skeeter make a wedge for between the motor and JP to change the angle to help this? I know my 21i has one, might try that.

  3. Member
    Join Date
    May 2015
    Location
    Zwolle, LA
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    2,436
    #3
    Was the new Jackplate mounted in the same holes as the old one? What was the PTP on the old jackplate?
    Bill Perry
    Zwolle, LA (Toledo Bend)
    bpicinc_2000@yahoo.com
    2001 ZX-250 VMAX 225. HDS-9 Carbon, HDS-7Carbon, 3D Sonar, HB 998c hd si, Active Target, MG Tour Pro 36v, 12" Slide Master
    USN, USS Newport News CA-148

  4. Member
    Join Date
    Jan 2021
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    3,513
    #4
    Quote Originally Posted by bpicinc View Post
    Was the new Jackplate mounted in the same holes as the old one? What was the PTP on the old jackplate?
    What I was going to ask. If set at old PTP height nothing really changed, it should handle the same.
    2008 Skeeter 21I. Yamaha 250 Series II.
    2011 Toyota Tundra Crewmax 4x4.

  5. Member
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    Mar 2010
    Location
    Bailey, NC
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    80
    #5
    My mechanic put the jackplate and motor back in the same holes as the original setup. PTP was 4.0" before the old jackplate was replaced. I am at 8 dots on the jackplate as before.
    There is a factory wedge that is used on my setup.
    I will try moving the PTP to see how it affects the holeshot and porpoise.

  6. Member utinator's Avatar
    Join Date
    May 2005
    Location
    San Antonio, TX
    Posts
    5,494
    #6
    Are the wedges turned the same way as before the jackplate swap? If they are upside down from before, then that will drastically change the trim angle. Your trim could be way different than you think.
    Gitcha Bass On!

    2015 ZX225

  7. Member skeeter21i's Avatar
    Join Date
    Dec 2008
    Location
    new summerfield tx
    Posts
    410
    #7
    drop to 4 dots see if it plows water it should then start going up 1 dot at a time until it starts porpoising then go down 1/8 of a dot at a time until it stops then you are done

  8. Member
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    Mar 2015
    Location
    Bixby, OK
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    2,280
    #8
    I have the same boat and if you're at 8 dots on the jack plate, your PTP is not 4". If the motor is mounted in the second set of holes (from the top), PTP at 8 dots is 2.5". I run mine at 9 dots with a worked 25 Tempest and have 0 issues with porpoising. Sounds like you're trying to trim too high for the speed you're going. Mine will stay on plane at 21 mph with the motor trimmed all the way down and not porpoise at all. If you're trimmed up and running fast and suddenly slow down without trimming down, it will porpoise every time.

  9. Member
    Join Date
    Mar 2010
    Location
    Bailey, NC
    Posts
    80
    #9
    Thanks for all the help guys, I am getting out this week to run and test at different settings. I can get it to run good by myself but then when the boat is loaded with water and both tanks full with a partner, the weight issue affects the holeshot and porpoise issues. Will post numbers as I get it dialed in.