Prop Recommendation

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  • #16
    Well that is interesting, your the first person I know of that has actually run the Sharrow props.
    I have a feeling that transducer you mentioned is causing some issues with all these props.

    As for your question about diameter, it makes a little difference, but that fact that you are 30++% slip with everything you try, it just sounds like the prop isn't getting clean water.
    Are you just trimming the motor way up to get the RPM, but no speed? or are you actually finding the best speed at that RPM?

    Ken Reeves
    [email protected]
    941-735-5808

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    • #17
      Well the way the transducer is it would be very easy to disconnect it from the bracket that attaches it to the transom even with the boat in the water. The bracket does not stick below the bottom of the boat. I could then make some runs and see if there is any change.

      I have not trimmed the motor up at all for any of these tests. I have left it down to know the motor was set up the same for each prop, dont know if that was a mistake or not. I am sure each prop could have even higher RPMs if I had trimmed.

      The Sharrow props are pretty interesting. I am going to try the fourth one this weekend. Turns out my boat fills a gap in the test boats they have access to on a regular basis. They have a variety of smaller boats, and one larger with twins but not a center console with a big single. Its been fun, and gives me an excuse to to rip around for a bit.

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      • #18
        The transducer I was most worried about was the one that was a through hull.
        but if its a really low profile, maybe its not the issue.

        And yes, even more strange that the slip is this bad with no trim, how high is the motor mounted?

        Ken Reeves
        [email protected]
        941-735-5808

        Comment


        • #19
          The motor is in the 3rd hole down from the top. When you put a straight edge from the keel the ventilation plate is about 1/4 to 3/8 above the keel. I have not looked at how the ventilation plate looks while the boat is underway yet. I have either been out by myself or with my kids. I am going to try and get out with a buddy this weekend so I can look and take some pictures.

          With most of those props it was hard to get the prop to ventilate. I was taking some really tight hard turns at high speeds that I would never due under normal circumstances and most never ventilated.

          The thru hull ducer is 3.5 ish inches in diameter and sticks down maybe 1/2 and inch.

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          • #20
            This is the style of the abandoned thru hull transducer.

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            • #21
              Well, having 30% ++ slip on a 25 ft boat without trimming the motor, banging the rev limiter with every prop you try, and all of them going within 1 MPH of each other regardless of style, or pitch is odd.
              Something is off.
              Your motor height description actually sounds low. would make a boat handle poorly, but normally wouldn't make the slip crazy high.
              Your not trimming the motor, which is definitely odd, but again, would not normally make your slip abnormally high.
              You say you've checked the tachometer, so we'll assume that is correct.
              You say you have used two different GPS devices, so I'll assume that is correct.

              I would attempt to trim the motor correctly with any of these props. See if your speed improves when you actually trim the motor correctly.

              That transducer can definitely cause issues. Its a pain to move it, but there is definitely a possibility that its causing issues.

              Ken Reeves
              [email protected]
              941-735-5808

              Comment


              • #22
                Hey Ken,

                So i was asking around and a friend of a friend had a 17p Thunderbolt that I borrowed this weekend. There is a lot to like about that prop. It did better in the slip department than anything I have tried yet. Cruise was a little slower than than the 19p rev4, which had the fastest of the ones i have tried. I really liked how responsive the thunderbolt was when you would hit the throttle. I have no idea why the slip numbers are still high, I guess when I pull the boat for the season in about a month or so I can take a look at the bottom and see if there is anything going on as you suspect. Here are the numbers I got this weekend, if anything the MPH might be 1 to 2 mph low. I didnt have a huge window of time to sneak out and it was pretty windy and tide was kicking today. I went in opposite directions and took the average of 2 runs to try and compensate. Again I did not trim up at all just to be consistent with the others.

                RPM - MPH - Slip
                2 - 8 - 56
                3 - 11 - 60 (stern really dropped down)
                3.5 - 15 - 53
                4 - 19 - 48
                4.5 - 27 - 34
                5 - 33 - 28
                5.5 - 37 - 26
                WOT (6) - 40 - 27

                It's amazing, like you said before everything is almost the same for each prop numbers wise. They all feel very different getting to those numbers but seem to end up the same. Is there anything else I can try to figure this out that you can think of? Seems like I may be in a holding pattern until I pull the boat and refresh my memory as to whats exactly is going on with the bottom. Being a new to me boat I am kicking myself for not taking a few pictures of it, oh well.

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                • #23
                  If you still have the prop, I would absolutely hit the trim button and experiment to see what happens.

                  Ken Reeves
                  [email protected]
                  941-735-5808

                  Comment


                  • #24
                    I still have it. The owner is not in a hurry to get it back. Won't the RPMs increase? Hey never know, I will give that a shot and see what happens. Probably won't get out until the weekend, work this week is busy and the sun sets so early these days.

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                    • #25
                      What Make 25 is this? What year?
                      Engine Sales and Service
                      Ph +1 954.463.1515
                      Fx +1
                      954.463.4904
                      Toll Free: 800.622.6747

                      [email protected]
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                      Member of the MSHS Group

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                      • #26
                        It's a 1976 Mako 25

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                        • #27
                          Originally posted by Fandarr View Post
                          It's a 1976 Mako 25
                          If you don't mind, without me reading the whole thread, what are you trying to accomplish?
                          That year Mako and size is not known for much along the lines of speed and economy.
                          Engine Sales and Service
                          Ph +1 954.463.1515
                          Fx +1
                          954.463.4904
                          Toll Free: 800.622.6747

                          [email protected]
                          www.parkeryacht.com

                          Member of the MSHS Group

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                          • #28
                            I am just trying to find a prop that will be a good all around prop. I am not super concerned with top end speed because I rarely run at WOT. Something that will give me a fast and efficient cruise is more important to me. It seems like each prop I try the RPMs and speed only vary only slightly even though many of the props have been very different from one another, and the slip numbers have been very high. The RPMs with almost every prop are right at the motors rev limiter. Ken has been helping trying to figure out why that may be and has a few theories that i am going to look into.

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                            • #29
                              If memory serves me correctly, the boat was never really designed for a single. It needed twins.
                              We put a 300 Four Stroke o one up here, guy likes it, but it doesn't go out much.
                              Heavy bote, especially if the foam is wet.
                              Engine Sales and Service
                              Ph +1 954.463.1515
                              Fx +1
                              954.463.4904
                              Toll Free: 800.622.6747

                              [email protected]
                              www.parkeryacht.com

                              Member of the MSHS Group

                              Comment


                              • #30
                                I surely have wet foam that is a given. The boat is rated for 300 hp and many guys that run twin 150s on it see similar numbers as single 300s, atleast the guys over at classicmako. Originally they could have been bought with twins or a single from the factory. I am not looking for a speed boat like I said, just a good all around performer. I really liked the Thunderbolt Ken recommended and the Rev4 I borrowed from a friend, which is basically the Q4 Ken recommended but it was a different pitch. The rest I tried were just eh. I guess what suprised me and Ken even more was how bad the slip was and high the RPMs are. With both the Thunderbolt and the Rev4 the boat was actually pretty quick and responsive, much more than I expected. I just didn't expect to hit pretty much 6k RPM with any prop I tried and its been everything from a 17p to a 21p.
                                Last edited by Fandarr; 10-20-2020, 07:55 PM.

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