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Upgrade 23" Tube to 25"

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  • Upgrade 23" Tube to 25"

    Hello all,
    Need some advice (or information).. I'm upgrading my toon from 23" tubes to 25" with lifting strakes and ne V-shape. Currently, my toon sits in the water with about 3/4 of the tube below the waterline. I have the 23" tubes and I believe these are old school and time for an update. My question is, what should I expect with these larger diameter tubes and lifting strake? Would I need to move or shift any weight such as seating? How much additional lift do you actually get with the strakes?

    Thanks ....

  • #2
    I'm certainly no expert but I'd bet if you're that low in the water then you may have way too much weight in the tail end. Such as water-logged furniture, carpet and deck. How does the bow sit at rest? Maybe shift some weight? I found water in my logs and still didn't sit that low.

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    • #3
      Going from 23" to 25" will be a lot of difference in my opinion. If you have the room up front, moving the fence and all your furniture forward a foot or so, or moving the engine pod forward a foot or so can make big differences too.

      I don't have a clue how you would predict just how much though.

      Are you planning on redecking the boat as part of your project, or just swapping out the 'toons? Are the new toons the same length? Are the mounting tabs in the same place?

      Finally, I might have a tendency to check out some later model boats that are equipped with 25" toons and have layouts and power similar to yours, to help get a sense for what works.

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      • #4
        Thanks all.. To ahicks, I recall we have corresponded recently and shared much info on our toons. Well, I completely did a rotisserie restore on the toon 3 years ago. New decking (Sherman XL deck) new carpet and a complete new interior (Premium). I love the seats and the decking still looks brand new. I made a somewhat major change by switching out the front wrap around with buckets, the wrap around were about 50LBS each whereas the buckets are about 25LBS (Full seating in the stern). The real weight difference is in the motor and location. I went from a 50HP SPL Johnson to a 90HP Merc (2-stroke), plus I installed a powerlift which set the motor back 5 in.. So the real difference is the motor: 115 LBS heavier and setback 5". Excellent point on moving things forward. I purchased a chain scale and before I begin this new undertaking, I'm scaling the bow area just behind the playpen, then I'm moving the motor forward 7", then scaling once again. The difference in weight should give me an idea if I have to move the entire fencing and interior forward and how much. My calculations are, I may need an additional 120LBS forward at around where the Playpen is. Once I get the scaling done, I'll add the new toons and get as close to that weight up front. Now the new toons, I got lucky, bought a pair online. They are the "new" engineered variety, "V-Shaped" with lifting strakes through the entire length of the toon. Because of the additional 2" circumference of the toon along with the lifting strakes, I'm wondering if I should add that much weight forward. I looked at many of the new pontoons and they all have certain similarities, such as less playpen up front and a small deck at the stern. So it appears manufacturers have moved the fencing and interior forward and set the motor back.
        Last edited by jbcurt00; October 2nd, 2017, 11:43 PM.

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        • #5
          According to my quick math, if the new logs wieghed the same as the old ones, the bottom 5/8 or so of the logs would be under water to provide the same lift as the old ones. If they weigh more (as I would expect), there may be little visible difference between how low the new and old logs sat in the water. I have no experience with strakes to share.

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          • #6
            Tommy, so you are saying all else being equal, with his 23" floating at 3/4 submerged, going to 25" would float the boat at about 5/8 submerged? Or am I missing something?

            PBX, Is the front of the boat floating at the level you want it, or does it need to come up as well? I like the idea of getting the engine forward to near where the original was. Is there potential to move further than that?

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            • #7
              Great questions.. As it sits now, The very tip of the front of the Pontoons are about 3" above the surface of the water. Out of the factory, the very tip of the Pontoons were just touching the water's surface. So, with the seat change, motor change and setback, the toons are about 3" lower at the stern and about 3" higher at the very tip. In theory, that makes sense depending on where the actual center of gravity is/was.. I had a 130lb female stand just behind the playpen, against the fence/door. By doing this the front dropped enough to set the very tips of the pontoons on the surface of the water (as new). So, (in theory), I assume I need 130 more lbs more forward and hoping to accomplish the weight distribution by moving the motor/POD forward. Makes sense right? But now introduce the 25" Pontoon w/lifting strakes.
              Do I need to add that much weight forward? Perhaps just moving the motor and POD forward 7" is enough. With the old 23" pontoons, I was thinking moving the motor, POD, seats and fencing forward 7" to 10". Not sure if that would be necessary with the new 25" and lifting strakes.

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              • #8
                ahicks - yes, that's what I was saying.

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                • #9
                  I read somewhere that the correct center of gravity for any Pontoon is just behind the helm. I'm going to check this out. My Pontoon is out of the water for the year and in a heated shop ready for the next project. Should be interesting where I find the center of gravity right now. Also, when I move the motor and POD forward, I'll post the weight differences here, this might be useful info for the next project.

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                  • #10
                    I think your right.. I'm only going to move the Motor and POD forward.. After installing the new Toons, and completing the entire project, I'll scale the front of the Pontoon. This will be interesting to note the difference, particularly when it goes back in to the water. Didn't think I needed an engineering degree to finish this up.

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                    • #11
                      Originally posted by HotTommy View Post
                      According to my quick math, if the new logs wieghed the same as the old ones, the bottom 5/8 or so of the logs would be under water to provide the same lift as the old ones. If they weigh more (as I would expect), there may be little visible difference between how low the new and old logs sat in the water. I have no experience with strakes to share.
                      I'm not certain this would theory would apply.. At the same weight the 25" tube would float higher because its dispersing more water and has greater volume of air inside. Spread this additional volume across 22' I may think that is substantial. My best guess.

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                      • #12
                        I also read that the difference between a 23" tube and a 25" tube equates to 500lbs of weight. So, in theory, place 500lbs of weight distributed across the entire length of the tube, the 25" tube would sit in the water at the same level that a 23" would with no weight at all.

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                        • #13
                          pbxcomm -
                          There's an old saying in engineering that goes, "Measure with a micrometer, mark with chalk and cut with an axe." The point is that no result can be more accurate than the least accurate element of the calculation that yielded it. Given your description of "about 3/4 of the tube below the water line," I didn't bother describing all the geometry and calculations I used to figure the displacement of 23" and 25" logs. I figured 5/8ths was accurate enough. But that answer was based on mathematics and the assumptions I described and was not just a wild guess. .... BTW, since your logs have a round cross section, know that the amount the waterline will move is affected by more than just the weight they carry. If the waterline is near the center of the logs when you add or subtract weight, you will see relatively little movement in the waterline because that is where the log is widest and displaces the most water per inch of depth. But if the waterline is either very high or very low on the log, then changes in weight will produce a much larger movement in the waterline as the log's cross section is much narrower there.

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                          • #14
                            Tommy, thanks for your reply..
                            Makes perfect sense..
                            To add to this, the new tubes are V-shaped not perfectly symmetrical or round. So, according to your calculations, are you saying that the 25" logs should float approximately 1/2 higher than the 23" logs, is that correct?

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                            • #15
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                              pbxcomm,
                              Not knowing the exact dimensions of the old and new logs the best we can do is guesstimate. And your guess is as good as mine. ..... Here's one more set of concepts to consider.
                              • The volume of water displaced by any boat is that amount equal in weight to the boat.
                              • The amount of water displaced by two pontoon logs is equal to 2 x the length of the logs x the cross sectional area of the portion of each log beneath the water. (This assumes the boat is sitting level and still in the water).
                              • The cross section shape of the logs will determine where the waterline is relative to the top and bottom of the logs, but it will not affect the size of the cross section of beneath the water.
                                • For example, the bottom of a tall, narrow log will sit deeper in the water than that of a round or short, wide log. But the cross sectional area that must be pushed through the water will be the same for both.
                              • Consequently, putting larger diameter logs on your boat may raise the height of your deck above the water, but it will not likely change how fast your motor pushes your boat. ... Of course the strakes may make a significant difference.
                              Last edited by HotTommy; October 3rd, 2017, 08:52 PM. Reason: Typo

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