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    Smart Tab/prop change lost RPMs-gctid375757

    So I went from no smart tabs and 14.25x21p prop WOT was at 4400. Added smart tabs and dropped to 14x19p prop and now WOT is 4100. I have the tabs still in the middle I did pick up about 3mph already. I can tell by the wake that the tabs probably are not coming all the way up but technically the 19p should have taken me closer to 4800 RPM so I'm 700RPM less than expected. Can those tabs really be holding me back that much?

    #2
    Maybe - and this is pure speculation - your Smart Tabs actuators are oversized. I don't know what the consensus is for your boat, but for the 175 it is 40 b actuators (for Smart Tabs SX), despite the general guidelines from Nauticus that recommend 60 Lb actuators for a boat that size. I've read in this forum where 175 owners have bought 60's and swapped them out for 40's.

    If you ultimately do conclude they may be ove-rsized, give Nauticus a call - they are very easy to work with for this kind of thing.

    Comment


      #3
      qbayle wrote:
      So I went from no smart tabs and 14.25x21p prop WOT was at 4400. Added smart tabs and dropped to 14x19p prop and now WOT is 4100. I have the tabs still in the middle I did pick up about 3mph already. I can tell by the wake that the tabs probably are not coming all the way up but technically the 19p should have taken me closer to 4800 RPM so I'm 700RPM less than expected. Can those tabs really be holding me back that much?
      Did you replace the prop with the same style/type as before i.e s/s, 3 blade??

      Did you have the leg trimmed to the same spot as before when you got 4400?

      Another way to check if it is the smart tabs is to remove the actuator and tie them up out of the way.

      Then take it for another run.

      Hope this helps.

      Comment


        #4
        I changed the smart tabs setting to the lightest, I'm heading out today i hope to give that a try.

        Comment


          #5
          Okay I'm probably fine, I went out with the tabs on the lowest setting and had another 170lbs onboard and was 38mph and 4550 rpms.

          Comment


            #6
            fish21121 wrote:
            Maybe - and this is pure speculation - your Smart Tabs actuators are oversized. I don't know what the consensus is for your boat, but for the 175 it is 40 b actuators (for Smart Tabs SX), despite the general guidelines from Nauticus that recommend 60 Lb actuators for a boat that size. I've read in this forum where 175 owners have bought 60's and swapped them out for 40's.

            If you ultimately do conclude they may be ove-rsized, give Nauticus a call - they are very easy to work with for this kind of thing.
            I picked up teh Smart Tabs as you recommended in another thread but I used their calculator and ordered the 60lb for my '06 175. You're saying that the 40lb's are better suited for our model? Curious as to where you heard that and besides a 50% increase in the lift, what is the differecen in performance?

            Frank

            Comment


              #7
              Fruffy42 wrote:
              I picked up teh Smart Tabs as you recommended in another thread but I used their calculator and ordered the 60lb for my '06 175. You're saying that the 40lb's are better suited for our model? Curious as to where you heard that and besides a 50% increase in the lift, what is the differecen in performance?

              Frank
              Most believe the 40's retract better on a 195 or smaller, despite their chart. The water pressure is meant to contract the actuator based on it's weight and speed. If the actuator is too stiff, it won't retract, creating drag. The Smart Tab is meant to "close" a bit so the tab is more or less parallel to the water, creating an outrigger effect. Good for turning (reduced chine walk).

              The Epic thread (archived at the top of this Forum) has plenty of testimony to this.

              Comment


                #8
                Fruffy42 wrote:
                I picked up teh Smart Tabs as you recommended in another thread but I used their calculator and ordered the 60lb for my '06 175. You're saying that the 40lb's are better suited for our model? Curious as to where you heard that and besides a 50% increase in the lift, what is the differecen in performance?

                Frank
                Frank,

                Smart Tabs were designed to be installed on a flat transom, where the tab plate hinge bracket and the upper actuator mounting bracket are mounted in the same plane. The actuator size recommendations are based on this "standard" setup. However, the 175 has a unique "bubble" protruding from the top half of the transom, which causes the upper actuator mounting bracket (attached to the bubble part of the transom) to be located more over the top of the tab plate. If you work out all the actuator force vectors for a 175 Smart Tab installation and compare it to a "standard transom" Smart Tab installation, it would show that a given actuator will exert more downward force in the 175 setup, because the actuator is nearly perpendicular to the tab plate. See the picture of my transom & tabs. Imagine if the "bubble" wasn't there. The upper actuator mounting bracket would be much farther forward, the actuator would be more angled in relation to the tab plate, and hence not able to leverage as much downward force. I believe this is the main reason why 40's are recommended for a 175 hull instead of 60's, contradicting Nauticus's general guidelines..

                The other effect of this setup is that the stock "double hole" clevis fitting on the bottom end of the actuator, that connects to the tab plate, will not provide the required range of motion to allow the plate to fully rotate up parallel to the water. The bottom shoulder of the clevis will interfere with a a shoulder on the plate before the plate reaches parallel to the water. Can you lift the plate up with your hand all the way such that the plate is parallel to the bottom of the boat? If you can't, the tabs will function like an airplane wing flap at planing speeds. You'll get plenty of stern lift, but also a good deal of braking drag. For Smart Tabs to work properly on a 175 and fully deploy upward when planing you MUST install the special single hole clevis fitting for the actuator/plate connection. See the attached picture of the standard double hole fitting (left) and the single hole fitting. If you call Nauticus and tell them what boat you have and what fitting you need, the will ship you a pair for free. They did for me. Others have reported similar excellent customer service in asking to exchange 60 lb actuators for 40 lb actuators. Those posts are a few years old now, so I wouldn't say that is a sure-fire thing, but worth a try.

                Nauticus provides all sorts of precise figures for performance improvements, but who knows if they are exactly correct. You'd need to have a lot of instrumentation and conduct multiple runs under identical conditions to prove or disprove them. What I do know from 1 season of experience with them is that they significantly improve performance in a number of areas. Not a little. A lot. The change is very noticeable: Much less bow rise coming up on plane. Reduced time to come up on plane. The boat just comes out of the water with much less effort. Lower minimum planing speed by a couple MPH. Greatly diminished up and down "chopping" motion of the bow when planing through waves (my kids - permanent inhabitants of the bow area - will verify that). Large reduction (but not elimination) of annoying bow wander at slow speeds. I don't run all out very much, so I've never bothered to compare top speed performance. As far as the claims for improved fuel economy...who really knows? With all the other advantages, I don't care much. IMHO, Bayliner should be equipping 175's from the factory with Smart Tabs SX installed, they are that good.

                Attached files http://baylinerownersclub.org/media/....jpg[/img] http://baylinerownersclub.org/media/....jpg[/img]

                Comment


                  #9
                  Thank you would be an understatement. Jim and tbear, That was truly informative and I appreciate it. Received the Smart Tabs yesterday and the end fittings today. Sending the 60's back for the 40's. Customer service still pretty ood. No problems at all.

                  Looks like I'll have to mount the extra bracket for transom tie-downs on the trailer.

                  Comment


                    #10
                    Jim,

                    Where did you get those brackets for the tie downs mounted to your trailer? I am planning on installing Smart Tabs but they interfere with the stock tie down location.

                    Comment


                      #11
                      nvrstsfd1 wrote:
                      Jim,

                      Where did you get those brackets for the tie downs mounted to your trailer? I am planning on installing Smart Tabs but they interfere with the stock tie down location.
                      nvrs,

                      I made the brackets from a piece of 2" angle iron from Lowes, a can of hammered silver Rustoleum, and a pair of u-bolts from Eastern Marine Trailer Parts Superstore http://www.easternmarine.com/ which just happens to be a few miles drive from my house. Several 175 owners here have reported simply replacing the frame bolt on the trailer rear bunk bracket with an eyebolt. I tried that, and I wasn't totally happy with it, as the tiedown straps have to take a very sharp bend around the end of the bunk board, are difficult to get tight, and the arrangement provides very little restraint for side-to-side hull movement on the trailer. I looked all around for some type of bolt-on padeye with no success, so I finally just made the angle iron brackets. I didn't have a drill bit big enough for the tie-down hook hole, so I drilled those holes as big as I could and then ground them larger with a Dremel.

                      If you want to put the tiedown brackets where I have on the trailer, make sure you mount the tabs on the transom a bit outboard from where the Nauticus instructions guide you. If you follow the Nauticus instructions precisely (I think they say 4" from the side edge of the transom), you may not end up with enough space for the tie-down strap to run between the inside edge of the tab plate and the trailer bunk board. Look at my transom picture to see what I am talking about. Instead of measuring 4" from the side of the transom, I lined up the outside edge of the tab hinge bracket with the knuckle chine line on the hull bottom, mostly for aesthetic purposes, but also to allow that little bit of room to use the tiedown brackets. I think either setup works fine as far as the tab functionality is concerned.

                      Please let us know what you think of the boat's handling and performance after you've had a chance to take her out for a spin with the tabs.

                      Regards,

                      Jim

                      Comment


                        #12
                        Jim, last question, I promise. Well..maybe.

                        I understand the new end fittings needed to attach the piston/ rod to the Smart Tab itself. What I don't understand is, when the transom "bubbles" outward as you described, how does the flat bracket mount on that rounded surface?

                        Comment


                          #13
                          Fruffy42 wrote:
                          Jim, last question, I promise. Well..maybe.

                          I understand the new end fittings needed to attach the piston/ rod to the Smart Tab itself. What I don't understand is, when the transom "bubbles" outward as you described, how does the flat bracket mount on that rounded surface?
                          Fruf,

                          I'm happy to answer any questions that I can. Much of what I've learned so far has come from others on this board, so it's payback.

                          You are right, the bracket doesn't fit precisely flat on the transom. But the base of the bracket mount is relatively small, and the curvature of the "bubble" is relatively large. So it's pretty close to flat. Close enough, especially if you bed it in 3M 4200 or 5200. This will also provide a bit more strength and stability. You definitely don't want that bracket "working" over time. Just wipe off the excess adhesive sealant around the perimeter of the bracket edge before it cures. I did the same for my tab hinge plates. You can do that or just use adhesive sealant in the vacinity of the screw holes, either way will work.

                          We put in at the Stemmers Run boat ramp at the end of Pond Neck Road in Earleville, Cecil County MD. Any chance I'll see you outhere on the Elk, Bohemia, Northeast, or Sassafras Rivers this season?

                          Jim

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