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What can I do to help stabilize my boat?

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  • What can I do to help stabilize my boat?

    I have a 16ft lowe line v bottom with a 40hp merc. I just finished rebuilding the motor and have decked the boat, carpeted it all, and built a side console. I have taken it to the lake twice and run it, and it has scared me a little bit with its handling at higher speeds. Higher speeds meaning at WOT, which is about 20mph. The motor has a Doel-Fin hydrofoil already on it, and I do think it helps with stabilization at lower speeds, so I will probably leave it on. When I am cruising around on the lake the boat leans quite a bit especially on turns, and it sharply shifts when weight barely moves on the bow. Its a bit unnerving when it does this, especially to passengers. I have been looking into these SX Smart Tabs and they seem like they be the solution, but I am not sure. Any advice is appreciated. Also, if anyone has experience with those trim tabs on a boat similar to mine, that would be awesome. Thanks. Mac.

  • #2
    Re: What can I do to help stabilize my boat?

    First thing i would to is to ditch (ok, simply remove...) the hydrofoil. It work wonder on some rig but can also be a nightmare on others or simply been inefective. On plane, the anti-cavitation plate (thus the hydrofoil) is out of the water. If yours is barely out of the water when on plane, then the foil will catch on any slight turn or weight balance and cause a sharp shifting like you describe.

    So try removing it before spending on anything else.

    1991 Boston Whaler Outrage 17 I
    2005 Evinrude E-Tec 90hp

    Fishing isn't a matter of life and death.... It's much more important.


    • #3
      Re: What can I do to help stabilize my boat?

      sounds to me you are not trimmed up and plowing thru the water with the whole hull in the water not quite on plane.
      I would try to trim the motor up to get more of the boat on top of the water and less plowing thru.
      I had a 18ft aluminum boat with a 115hp and found the boat ran alot better with only the minimum amount of hull in the water at speed. Too much and it would dig into one side and be unstable.
      sigpic 1981 Glastron SX-190 300hp 350 SBC
      Living the Dream


      • #4
        Re: What can I do to help stabilize my boat?

        It does get on plane fully. I have run it with and without the hyrofoil and it seemed to me to be more stable. Also, it is a manual trim motor, and I have it on the lowest pin setting. I have tried other pins, but it did not get on plane on those other settings.


        • #5
          Re: What can I do to help stabilize my boat?

          Have a 16.5 alumacraft with mariner 40 power trim, It runs about 25 wot. Very stable in turns unless you turn to quick then it cavitates. Have a dolfin on it, planes very nicely. Will run hard chop on lake erie great at wot cutting top of waves much better than without dolfin.


          • #6
            Re: What can I do to help stabilize my boat?

            It may just be the nature of it. That's a small, light weight boat. It doesn't have alot of mass, and moving mass around in it (passengers moving around) will have an effect on it listing from side to side. Growing up, we had a 14' aluminum with an 18 hp merc on it. I swear every time we were out on it, my father would yell at us to "stop getting up and going for a walk" about 20 times a day. Mind you, we were 40 - 50 lb kids, and we weren't getting up and going anywhere, but rather fidgiting from side to side. It was unerving, but looking back on some of the boat wakes we took (fishing St Lawrence shipping lanes), it really was a stable boat.
            Jon Hunter
            Marion, NY

            2006 Procraft 200 Combo with Merc 200 Opti
            2007 Homemade Duck Boat with Merc 39


            • #7
              Re: What can I do to help stabilize my boat?

              So will those smart tabs help or will I not notice a difference? I understand if that may just be the nature of the boat, but I have always known those deep and wide v bottoms to be pretty stable boats, and mine just seems like it should be a little less tippy. I'd just really like to do something to help it if possible.


              • #8
                Re: What can I do to help stabilize my boat?

                You say you "decked" the boat and built a side console.

                Did you raise the deck? Add a raised casting platform ?

                Sounds like you added a bunch of weight to the boat AND raised the center of gravity.

                A 16' aluminum with a 40, and it doesn't get on plane, something is wrong.
                Medford, WI


                • #9
                  Re: What can I do to help stabilize my boat?

                  I would think a 16 would handle the added weight ok.
                  There may be too much weight at the bow.
                  I think you need to get a lower pitch prop.Look for the numbers near the base of the blades or under the prop nut.Running trimmed in all the way is very likely driving the bow down into the water which could make it swerve strangely when you turn.
                  See if you can weigh some of the scraps from the materials try to figure how much weight you have added.It would really help if you had a tach and a gps to get an idea how its really doing. If your deck is at seat level it raises the center of gravity and when you stand near the edge its more like you were standing on the gunnel.
                  Get those prop numbers We need to get the bow up and still be able to plane.
                  Also check the height of the motor.The antivent plate(just above the prop) needs to be even with the bottom.


                  • #10
                    Re: What can I do to help stabilize my boat?

                    Okay, I will get that information for you to the best of my ability. When I say I decked it, I did add a raised casting platform over half of the boat. It is about 9 inches up from the floor. I Tig welded an aluminum frame with 1/8" thick 1.5"x1.5" sq tubing. Very light. Then I decked it with 1/2" outdoor plywood and carpeted it. I built a side console very similar to those on bass tracker boats, but maybe a little wider. From what I could find online, an approximate weight of a 4'x8' sheet of 1/2" thick plywood is 50 lbs. That being said, I probably added about 80-100 lbs of wood weight. I have a battery at the stern for my outboard, and a deep cycle in the bow for the trolling motor. Is it possible that this battery in the bow could be causing problems?

                    On the prop: 48 816704 A40 13P

                    And I am thinking by antivent plate you mean cavitation plate? It is perfectly even with the bottom.

                    I have also tried different pin heights on the motor mount to see if that helps it plane better, but maybe a little more trial and error is necessary.


                    • #11
                      Re: What can I do to help stabilize my boat?



                      • #12
                        Re: What can I do to help stabilize my boat?



                        • #13
                          Re: What can I do to help stabilize my boat?

                          I doubt that adding 100 or so lbs 9 inches above the factory deck height is going to make much difference in handling. I say that because I added 50 lbs to a 16' cuddy by adding a hard top to the boat. The boat is probably 18-20" higher than before, and all the weight is up high, about 3 feet above the deck. So if that mod on a 16' didn't mess up the handling, I doubt the weight you added will do it either.

                          I would look to the motor setup, maybe Smart Tabs will help. I have Smart Tabs, and they did improve performance because my boat got stern heavy with extra batteries and an added permanent fuel tank. They work well, but do add a little splash factor to the back of the boat. Now that I have a motor with power trim, I may remove the tabs.
                          sigpic 1985 Bayliner 1600 Capri Cuddy, 1965 MFG Niagara Custom. >> MFG Video<<. >> MFG Project<< >>Bayliner Hard Top Project<< >>Bayliner Repower Project<<


                          • #14
                            Re: What can I do to help stabilize my boat?

                            Just reading the thread - lean to agree that your CG is off. If it's constantly leaning to the same side as your console is on it's almost a sure bet. Your weight, plus the console pulling to one side, plus your new platform pulling forward (I'm guessing) - your boat is probably plowing through the water. Since the center of gravity is now more toward the front, when you turn the motor the thrust is pushing you more to the side (especially when you're turning in the direction of your console).

                            Pure guesswork, but I'm thinking it through on the 14' boat I'm used to.

                            Murfreesboro, Tennessee


                            • #15
                              Re: What can I do to help stabilize my boat?

                              It isn't leaning to the side of the console, it just leans when someone sitting shifts their weight. Maybe I'm just being too picky. I'll make some more runs and see what i think.