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How to install trim tabs on aluminum boat

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  • How to install trim tabs on aluminum boat

    I have a 2009 Starcraft Fishmaster 196 and I am going to install M80 Bennett trim tabs on it - Only one problem - I cannot get to the transom area to through bolt the trim tabs onto the transom. Starcraft refuses to give any information on the schematics of this area so I have to assume that the transom ,material here is .100 aluminum backed by spray in flotation. I spoke with Bennet and they insist that the through bolt should be used. I am trying to figure out a way the add more "substance to the aluminum in this area and I am thinking of bonding a piece of 1/8 to 1/4 aluminum to the hull with JB weld then using self tapping SS screws to attach the trim tabs - the screws would not only reinforce the JB weld but would also provide substantial support for the screws to hold the tabs on. Bennet says that this may work but will not "ok" the process,

    SO _ I am looking for input on this issue - has anyone ever attached tabs to the back of an aluminum boat and how did it work out. Any assistance and input is appreciated.


  • #2
    Re: How to install trim tabs on aluminum boat

    No way to get your arm in through the side of the bilge eh?
    No Current Boat.. :-(

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    • #3
      Re: How to install trim tabs on aluminum boat

      Click image for larger version

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      I think that the mounts in this photo were early options for mounting trim tabs....

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      • #4
        Re: How to install trim tabs on aluminum boat

        I would not use JB weld will not hold over the long term. I think your idea of add ing a alum. plate is good but you need to get bolts in it with washer and nuts on the back side. At the top of the plate you mightbe where the transmom is and could use 1/4" x 1-1/4 stainless lag bolts, make sure you seal them good so water does not get in to the wood and rot. You still need some bolts at the bottom and if you have no access I would say you are out of luck on putting trim tabs on.
        I thought of putting trim tabs on my ss, but did not. I make 1-2 POB's sit up front in the cab and store most of my lead fishing weights and stuff up front.

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        • #5
          Re: How to install trim tabs on aluminum boat

          This should not be much different than installing on a glass transom.The transom on both type boats is basicly the same . Providing the transom is good, measure ,pre drill holes, and coat the Stainless mounting screws to the transom. Sealed it should be ok. I have put the Bennett tabs on my 22 holiday just the same as my previous glass boats and no problem what so ever. The same with the pistons for the trim tabs mounted to the transom. Just be sure the screws are the right size and tight. The Marine Sealent should keep the water out of the boat. The only problem I can see is if a non compatable attachment is used that might be aggesive to the Aluminum.

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          • #6
            Re: How to install trim tabs on aluminum boat

            on my boat there's a gap of about 1.5" from the bottom of the boat to the bottom of the transom, leaving nothing on the back side. I think most of the trim tab torque on the transom will be pulling at the bottom.
            No Current Boat.. :-(

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            • #7
              Re: How to install trim tabs on aluminum boat

              On Bennett trim tabs the only strain on the botton piece is to hold the bottom on the boat. The strain or torque is on the Hydraulic Piston that raises and lowers the trim plate. The piston is mounted well up on the transom and thru the wood in the transom. The bottom is actually only a hinge for the tab to travel on.

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              • #8
                Re: How to install trim tabs on aluminum boat

                On Bennett trim tabs the only strain on the botton piece is to hold the bottom on the boat. The strain or torque is on the Hydraulic Piston that raises and lowers the trim plate. The piston is mounted well up on the transom and thru the wood in the transom. The bottom is actually only a hinge for the tab to travel on.

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                • #9
                  Re: How to install trim tabs on aluminum boat

                  Oh great one for each eye to read. SORRY

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                  • #10
                    Re: How to install trim tabs on aluminum boat

                    Well If the strain or torque was minimal then why is Bennet Recommending through bolting? and think about it, your trying to push down a boat weight 2000-4000lbs. I wont believe you until I see a full engineering analysis.
                    No Current Boat.. :-(

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                    • #11
                      Re: How to install trim tabs on aluminum boat

                      Whatever--- My 22ft Holiday has A load of weight in the boat. Only posted for advice that works for me with no problems.I run a lot of hours in the Pacific and the local river. I have 2 motors on the back a 9.9 4 stroke Merc and a large 200 hp Johnson 2 batterys and most of my downriggers (3) and 8 21 # weights all stored in the rear. Post what you find I may have My holiday over loaded. I run at high speed on most trips Prop is a 14 1/4 21 pitch , it ran to 50 mph with out tabs and I was able to drop thr RPM a little with tabs. The best to you on your project.

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                      • #12
                        Re: How to install trim tabs on aluminum boat

                        I wouldn't have thought you would need through bolting either. Puget you have tabs on your boat right ? are they through bolted ? I'm interested in some type of trim tab too..
                        No Current Boat.. :-(

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                        • #13
                          Re: How to install trim tabs on aluminum boat

                          Pugetsound - Can you please tell me exactly how you did it - Pictures would be great

                          I assume yo just used self tapping stainless screws?

                          What is the thickness of the aluminum at the mounting point - did you through bolt

                          PS __ JB weld says there bond is permanent and it will not loosen with water immersion. I bought some today and intend on doing some tests bonding two pieces of aluminum together

                          More to come

                          PS please keep you ideas coming

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                          • #14
                            Re: How to install trim tabs on aluminum boat

                            Guys , if its accessible and you want it to last I'd reccomend you rivet a 5052 doubler plate with solid 5052 rivets (blind rivets if inaccesible) and pro seal 870 or PR 1422 sealant between the hull and doubler (faying surfaces) , the larger the better up to a point as it will distribute the load and stiffen the transom skin as well. 2 1/2 to 3 diameter edge distance is a good rule of thumb with one inch rivet spacing. The attach your trim tab and actuator mount to the doubled area if possible with rivets or good quality hardware.
                            these are some pics from a fuel catch can I installed a while back in a bell 205 helicopter but it shows the general idea





                            In a time of universal deceit telling the truth is a revolutionary act.

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                            • #15
                              Re: How to install trim tabs on aluminum boat

                              I just asumed it was like any other boat. the 11inch adjustable tabbs are mounted with stainless steel screws. 5 hold the tab plate and three on each cylinder. 8 on each side. I also have two extra transducers mounted by just stainless screws. I did not realize there might be a problem in the future. the tab plate is level with the boat bottom, Never considered thru bolting. Perhaps your Idea is best. I have never had water in the bilge or have seen the bilge pump come on . Even if I should have shown more concern If it aint broke I won't fix it. LOL The boat is at our summer home in northern Idaho till spring.Otherwise I would send a few photos. There is a 21 ft Holiday Starcraft that uses our Skagit River with a jet pump and I noticed he had Bnnet trim tabs on his boat,

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