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    Inconsistent Props ??-gctid409412

    http://boatpropellers.iboats.com/Mer...t_id=213627214

    Confused

    I have 2 of these props and I ran the first one for almost 2 yrs before I found some bottom and chewed it up some

    In those two years, I got to know it rather well and it was perfect until I bruised it 3 weeks ago. When I'd put the hammer down to get on plane, it would fairly quickly get to about 4000 RPMs (3/4 seconds), I'd get on plane and back 'er down to about 3700/3800 RPMs and the boat was on it's sweet spot and that was where I'd ride.

    Now I have the new prop on and after 6 or 7 tries, it jumps past 4300 RPMs in a heartbeat (2 seconds maybe?) but it won't plane below maybe 3900 and that sweet spot is 4000 to 4100 RPMs

    So, what gives? Did my 2 y/o prop change it's angle of attack slowly over the course of 2 yrs, or is this new prop just set to a different pitch?

    Oh, I did dbl check the numbers stamped on each prop and they're identical

    Thanks for any insight on this,,,,,pretty weird stuff!

    Sarah

    #2
    Could be the amount of cupping in the bladed is defferent between the two props, or may be the amount of flex of the prop blades. You can have the cupping measured by your local prop shop, not sure how to inexpensivly check the flex characteristics of the blades. Could also be a design change by the manufacturer. I've seen many parts change over the years and the part number stay the same.

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      #3
      What type of Hub is in new prop? Plastic or older Rubber?

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        #4
        3 wide wrote:
        What type of Hub is in new prop? Plastic or older Rubber?
        Both of 'em use that Rubex piece in the middle,,, Rubex Hub is what it's called (I think)

        It's a separate, rubber center and I changed it when I switched props.

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          #5
          I'm fairly certain we have identical props. I can't confirm it, but I'm experiencing a similar issue. This is a second season with the Solas 4 blade aluminum prop I have in my signature and noticed boat needs much higher RPM to stay on the plain and cruise than last year.

          The bottom is clear, I even had a fresh layer of VC-17 coated this spring so there should not be issues. The prop hub is not spun as I marked the hub and prop with a small grove to check on it. I'm starting to think these cheap aluminum props deform under heavy loads (our boats are very heavy compared to other 24') thus changing blade geometry and pitch under load. I can't confirm this until boat is hauled out this fall, but I'm getting a stainless steel prop next season.

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            #6
            hhhmmm, interesting

            I don't know if I can ever bring myself to spend $350 on a prop

            Partly cuz I do tend to play around in shallow water and I've heard that a goof with a SS prop is really bad for my drive.

            I'm sure that I have been luckier than talented at not botching mine up sooner.

            I guess that props are kinda like MAD-SCIENCE

            thanks

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              #7
              try living in the colonies where a 4 blade ss prop is $1200, then you learn how to look out for it hehehehe

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                #8
                EwenM wrote:
                try living in the colonies where a 4 blade ss prop is $1200, then you learn how to look out for it hehehehe
                +1

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                  #9
                  they do flex..Sarahs new prop is flexing more than the old one.. ss will not much much if any..but you will turn less rpms.

                  [QUOTE=GrindKore;713316I'm starting to think these cheap aluminum props deform under heavy loads (our boats are very heavy compared to other 24') thus changing blade geometry and pitch under load. I can't confirm this until boat is hauled out this fall, but I'm getting a stainless steel prop next season.[/QUOTE]

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                    #10
                    Thanks guys

                    I knew that I wasn't imagining it

                    I don't know much yet, but I do pay attention!

                    Comment


                      #11
                      EwenM wrote:
                      try living in the colonies where a 4 blade ss prop is $1200, then you learn how to look out for it hehehehe
                      +1

                      Revolution 4 - 19"

                      Comment


                        #12
                        What size prop are you spinning? I would go to a Flow Torx system with stainless. I have a few props laying around and maybe somebody else could loan one to test.

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                          #13
                          Same issue here. 4000lb 21 ft boat, Merc. 260 Alpha. Spun the hub in the old 14 x 19 aluminum 3 blade, with a couple nicks in 2 of the blades. Bought a new Solas/Rubex 14.5 x 19 3 blade aluminum with hub. I gained 350rpm at cruise. Now to cruise at 25kts I need 3850 to 3900 rpm where the old prop had me there at about 3500 to 3600. The blades on the new prop are definitely thinner at the root.

                          Getting the old one fixed and rehubbed and will reinstall and keep the new one as a spare.

                          SS is not really an option in this area as there is far too much flotsam. I'll keep buying or fixing alloy props before I chance sacrificing a shaft or worse.

                          James

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