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Boat porpoising...

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  • Boat porpoising...

    I recently bought a used 17 foot boat called a vector with a 200 Suzuki outboard on it.When I take it out it always wants to porpoise real bad. I've tried different trim settings, and it is better when trimmed in but it still does it and the boat slows down when trimmed it. Somebody told me the motor height maybe wrong. I think the cavitation? plate is like 5 or 6 inchs above the bottom of the boat.Also I'm running a stainless prop that has 23 stamped in the side and when I get to 6000 rpm the engine starts to cut out. I guessing I have the wrong prop. Anybody know what kind of prop I should get.


  • #2
    Re: Boat porpoising...

    i had a problem with porpoising last weekend, i had to set the trim pin coser to the transom because i was 6hrs from home. i never had a problem with it until i started raising the motor up! a couple days ago i set the motor back down.

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    • #3
      Re: Boat porpoising...

      Try some trim tabs. That will and should help solve the problem.Do a search for a product called "smart tabs" I hear they work greatAlso weight distribution may cause porposing as well. Try more weight in the front of the boat.Any other thoughts?

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      • #4
        Re: Boat porpoising...

        what200,Five or six inches seems kind of high. What kind of boat is this? I'm not familiar with "Vector" boats.As mentioned, porpoising is usually caused by too much weight, in the stern.At 6K rpm. you may be up against your rev limiter. Check with a Suzuki dealer to see what the max rpms are.If you do end up lowering your engine a notch or two, your rpms will decrease.

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        • #5
          Re: Boat porpoising...

          You can also try a hydrofoil like Doel Fin or Stingray as well. I use both hydro foils and trim tabs. You can start with a foil for like $30 then add tabs if they foild doesn't completely solve the problem.

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          • #6
            Re: Boat porpoising...

            what200 Is that a Hydrostream, model Vector??If so, look at the pad and see if it has a slight hook in it.Possibly 5" is to high. Does it have a water cooling pressure gage, does the lower unit have a low water pick-up?Hydrostream has a web site that can help you with the set-up of your boat. Also visit Scream & Fly for good go-fast info.Good Luck,Gold Bear

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            • #7
              Re: Boat porpoising...

              A Permatrim hydrofoil will stop your problem. http://www.johnfjensen.com/permatrim_hydrofoils.html

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              • #8
                Re: Boat porpoising...

                Porpoising is a problem caused by weight balance. It is sometimes corrected or reduced by triming the motor as far down as possible. This method uses the prop to push up on the stern and rotate the boat forward applying more pressure on the bow to keep it down. Frankly, i do not believe in using the prop to correct boat handling and attitude problems, it is for propelling. If the motor is too high ( the cavitation plate on the motor should be even +/- 1" with the bottom of the hull V) the ability to trim the motor down and under the stern will be impossible. Therefore little or no help!Using a hydrofoil to lift the stern will help push the bow down, and can minimize porpoising depending on when the porpoising begins to occur. For example if the porpoising starts at 24 mph the amount of stern lift at that speed may not be enough to stop the porpoising. The hydrofoils provide increasingly more lift as the speed increases. If the boat is fast enough and the hydrofoil large enough the lift at higher speeds ( 35+mph) can cause too much bow down pressure which will eliminate the porpoising but create bow steering and excessive lean in turns, and lower top speed, and less fuel efficiency.Chek the motor height, check the max trim angle down, and look into trim tabs or Smart Tabs on this site.Trim tabs are adjustable to the water conditions (either manualy or automatic)and therefor do not cause other problems while trying to correct another. And they do not use the prop energy to correct handling issues. Translates into better fuel economy at any speed.
                Get SX Smart Tabs cosmetic blems for an extra $20 off (only $99.95) exclusively at iboats.com
                link: http://www.iboats.com/Nauticus_SX_Sm...2485--dz.54646

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                • #9
                  Re: Boat porpoising...

                  I tried it again recently but with a different prop this time. This prop has 28 stamped in it. It still wanted to porpoise a lot.Here's a pic of how high the motor is: I'm guessing the plate is about 7 or 8 inches above the bottom It kinda seems to me that a fin will be out of the water at speed. Are you guys sure that will help?

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                  • #10
                    Re: Boat porpoising...

                    From what you are saying and by the looks of the picture, it looks like someone set your outbourd up to try and run it like a surface drive. What I think is happening is that you are only getting the bottom half or less of the prop in the water when up on plane. The prop starts slipping causing the bow to start to rise. This alows the prop to get more bite as more is submerged causing the boat to lift out of the water again. It just keeps sliping and grabing over and over causing it to porpoise. This is just my opinion however. I think if you lowered the motor untill the cav plate was level with the bottom of the boat, you would fix most of it and also increase your top speed. The motor wouldn't be so apt to free rev as high, hitting the rev limmiter also.Again this is just my opinion.

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                    • #11
                      Re: Boat porpoising...

                      if it's a Hydrostream Vector you won't get anywhere until you put NITROUS on that Suzi. They won't turn over 6000 unless you put it on the juice. Won't need no afterplanes, plates, trim tabs. Motor will last about 30 seconds so be ready to fly, but it'll be a short trip.Good luck Dude

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                      • #12
                        Re: Boat porpoising...

                        Uncle Tony must give you all your outboard advice. Hey, it might last 40 seconds if you can find those fiber reeds for me. So how's the hydrasprouts project going for ya?Well, anyway, I got fed up and changed motors, but it still wanted to porpoise. Anymore ideas??

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                        • #13
                          Re: Boat porpoising...

                          Foils are for fishing boats...slow one's.......( . )( . )..........

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                          • #14
                            Re: Boat porpoising...

                            what200, i think you'd be happy with smart tabs, they will solve your porposing problem without comprimising speed.

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                            • #15
                              Re: Boat porpoising...

                              Man...that is a HUGE casting platform on the front of that boat Seriously, Smart Tabs transformed my boat. For the money, I recomend that for problems of porpoising or problems getting on/maintaining plane try the Smart Tabs first, and you will solve the problem. It is a rare thing that I buy something that turns out to be far better than I had hoped, but Smart Tabs were just such a purchase.

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