Increase prop diameter?

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  • Increase prop diameter?

    Good morning,

    I have a 2007 Skeeter zx22v (slightly deeper V than the skeeter zx22 bay) I believe it is a 20 degree deadrise. It has a 2007 200 Yamaha HPDI on it. Its on a 12" atlas Jackplate. Gear ratio is 1.86
    My estimated total weight for my usual fishing is 3800 lbs, boat, gear motor, fuel etc. (boat and motor we are at 2800)
    Current prop on it is the Yamaha 21P which from my research is 21 x 13 3/4
    The prop has some dings etc in it so Im wanting to change this one out and keep it as a spare/back up.

    Performance wise, its decent out of the hole- not great. Top end I am getting 49.2 mph (on gps) turning 5300rpm trimmed all the way up before she blows out. This is on fresh water inland. At the coast I get a touch more top end (around 51)

    I read about another ( slighly lighter bay boat) on THT that changed his diameter and it made a big difference in holeshot and top end while increasing rpms 300. I am wondering if a larger diameter prop or lower pitch will help me get out of the hole quicker and get me into the low 50's in fresh water. The HPDI says WOT is 4500-5500 so I am in the range. I have heard of others running these closer to 6000 rpm (limiter is at 6200??)


    Any feedback/advice would be greatly appreciated
    Last edited by googan205; 08-17-2021, 06:00 PM. Reason: edited the weight (from 3300 to 3800), added a jack plate and the deadrise.

  • #2
    Welcome.. I am sure Ken will check in soon and follow up.. Glad to have you.
    As of April 2nd, boatless for the first time in many years.
    2019 Tidewater 252 CC Twin F150's- SOLD
    2016 Tidewater 230 CC VF250 SHO- SOLD
    Mobile, Al.
    Dauphin Island, Al.

    Comment


    • #3
      Just thinking out loud...
      From my limited info, observations and little experience, I've usually seen folks try and swing as much prop diameter as they could get away with. The idea is, to push as big a column of water or air, with as little drag as possible. Unless the craft is a lightweight racing machine, with corresponding hull design and all of the considerations for the application...then you swing a bit less diameter and spin the heck out of it for velocity. These smaller props usually have more "slip" until the forward velocity approaches propeller speed. What is slipping is the smaller column of mass compared to the surrounding media, air or water. Larger prop diameters affect a larger area, but require more Hp to turn. They also have higher tip speed at a given RPM. Blade area and design also come into play. Rake, cupping, cleaver trailing edge, etc. You can go nuts chasing the "perfect prop". No such animal. They all have a range that they do their thing well. Outside of that design range, and the efficiency curve drops.
      Unless you are seeking full throttle maximum supersonic speed because you are racing...many folks are looking for static and midrange thrust. It helps keep you on plane at lower speed and is usually better in economy. The thinner the foil, the less drag.
      I've used ducted props on racing hovercraft, wood and composite on airboats, and aluminum and stainless on boats. I like stainless for boats or composite for airprops. Thinner foil, stronger materials.
      Just thinking out loud...
      Last edited by SeaCat22; 08-16-2021, 05:53 PM.

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      • #4
        Ok, so there were a couple 200 HPDI's
        the standard saltwater 200 HPDI, 2.6L and a 4500-5500 RPM range. Rev limiter is 5800 normally.
        they had the 200 HDPI VMAX, 3.3L which had a 4500-5500 RPM range in 2005, then in 2006 it went to 5000-6000 RPM range, and had a 1.81 gear ratio.

        Yamaha has a few props, if yours is shiny stainless, its either the saltwater series, (15 x 21) or maybe the Performance series, which is 14.5 diameter
        or maybe its the painted stainless, which is smaller diameter.
        assuming you have the 2.6, your slip numbers are not bad. 5300 at 49.2 is 13% slip.

        If the motor is revving up pretty easily when you initially hit the throttle, but the boat is just taking a longer time to come up, then yes, a prop with better traction would get you up and going faster.


        Might be worth having a little cup put into that prop to give it a little better traction and hold the bow better.

        Of the stuff I have available, I'd probably try a Powertech VMS3 in 21 pitch. that one is 14.6 diameter and normally has pretty good traction and lift.

        Ken Reeves
        [email protected]
        941-735-5808

        Comment


        • #5
          Hi Ken,

          Thanks for the reply.

          Mine is the 2.6 with the 1.86 ratio. I just went a double checked, The prop is actually the 21-M (not p as i had listed) so i think its closer to 21x15. Looks like the diameter would not make any difference.

          Do you have a VMS3 I can test? Would an OFX3 work? I see on powertech these are made for bay boats- which mine is.

          I would love to test a couple props and buy one from you. Plan is to keep my current one as a spare.
          Last edited by googan205; 08-19-2021, 03:54 PM. Reason: question about ofx3

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          • #6
            I don't have any powertech props to test.
            But if you buy one from me you can return it for 35 bucks.

            both the VMS3 and OFX3 are bowlifting 3 blades. either would do well, so would having a little cup added to your Saltwater Series 21

            Ken Reeves
            [email protected]
            941-735-5808

            Comment

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