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Thread: Need help with porpoising (no, not the mammal)

  1. #1
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    Default Need help with porpoising (no, not the mammal)

    Hey there, OOD brothers and sisters.

    I have had my boat (2018 Nitro Z19 Sport, 200HP Mercury Pro XS 2-stroke) for the last 2 years+ and have recently had issues with porpoising after getting on plane.

    It gets out of the hole just fine, but shortly after getting on plane, it starts porpoising pretty badly - even when I trim the motor up. I've been out 3 times this year and it has progressively gotten worse. Also, I don't know how much this factors in, but the trip out in the morning is usually okay, but the return back to the dock at the end of the day is significantly worse. It got so bad yesterday that I had to power down and crawl (just over idling speed) back to the dock

    I may end up having to take my boat into the shop, but would like to avoid that if the fix is a simple one.

    Any thoughts on what this could be and how it could be remedied?

    Thanks in advance for all assistance.

    Tight lines,
    T-S

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  3. #2
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    Sounds like a balance problem. I find the more I trim out the greater the porpoising especially in waves. Trim all the way down flattens the ride. Interesting on the difference on the way out as opposed to the way in. Could it be the difference in gas volume. less gas less weight different balance point. You got a live well in the bow? Try filling it to add weight out front my give you an indication if its a balance problem.
    Time in the outdoors is never wasted

  4. #3
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    Direction of wind and wave can affect porpoise too.

    Try trimming down.

  5. #4
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    It’s either a trim issue, or weight. My guess is trim. Trimming down will push the bow down, like others have said. You say it is worse, even when you trim it up.... that’s the wrong direction....you need to trim it down. Trim too high will also cause cavitation. Is that happening at all ??

    BTW....welcome to the forum !
    Last edited by rick_iles; July 10th, 2020 at 12:45 PM.
    “If you’re not a Liberal by twenty, you have no heart. If you’re not a Conservative by forty, you have no brain.”
    -Winston Churchill

  6. #5
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    Send a pm to sawbill. He has a good solution to this problem, but don't tell him I sent you.

  7. #6
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    Thanks to all of your for your views and suggestions.

    Here are some additional details in response to some of your questions:

    1. no live well up front;
    2. yes, I do get cavitation as well;
    3. the porpoising happens right after I get on plane - before I've trimmed at all (I'm trimmed down all the way for the hole shot).

    I will take your suggestions and try some of your propose fixes the next time I take the boat out.

    Thanks, all. I'll keep you posted.

    Tight lines,
    T-S

  8. #7
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    Odd it just started now and I’m sure you would have mentioned if you changed your prop but is it damaged? Anything you did to the boat from last year to the beginning of this? New down riggers or something significantly added to the rear adding weight (new fishing partner) [emoji2958]

    Let us know what it ends up being.


    Sent from my iPhone using Tapatalk

  9. #8
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    Quote Originally Posted by Bushmoose View Post
    Send a pm to sawbill. He has a good solution to this problem, but don't tell him I sent you.
    I know where you live.

  10. #9
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    Thanks, all, for your suggestions. I will try out various things on my next outing and see if the problem is alleviated.

    I will post a follow-up with any new development(s).

    I sincerely appreciate the advice.

    Tight lines,
    T-S

  11. #10
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    Good morning, All.

    Further to the great advice that I received in response to this post, I was able to get out on my boat and did some experimentation on the porpoising issue.

    True to everyone's advice, the issue was one of weight distribution. It was truly amazing to me that having a passenger sit a few inches to the left or right or having one or more of them lean forward could mean the difference between a nice smooth ride and a scary bouncing one!

    Thanks again to everyone for their great advice.

    Tight lines,
    T-S

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