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3 or 4 blade prop - which is better ?

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  • 3 or 4 blade prop - which is better ?

    which is better 3 or 4 blade prop, or does it even matter, as long as the right rpm is obtained ?
    Bring rain gear !

  • #2
    Depends on what boat you have and how you use your boat. Yes WOT rpm needs to be in the correct range for your engine.

    generally 4 blade will provide better hole shot , slow planing speed, and stern lift at the expense of top speed. I have run 4 blades on my last two boats because my general use is 6-7 people while towing a skier or wakeboarder. My boat is a bit stern heavy so for the way I use my boat I’m happier with a 4 blade.

    newer three blade designs lik,e laser two and enertia generally perform well in acceleration and top speed, both get good reviews on this site.

    bottom line best bet is to find a prop shop either local or on line who will let you try a few. I tried a pair of Michigan vortex 4 blades a few years back ended up buying both one for cruise one for skiing. These were inexpensive aluminum props that helped me cut my teeth on playing with props. I later Stepped up to stainless after I had honed in on what works for me.

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    • #3
      Three or four blades are just some of the design consideration. Really depends on your performance criteria or what problem your trying to fix.

      I went from an inexpensive 3 blade stainless to an OE 4 blade stainless then back to a “performance” 3 blade stainless of a different design.

      I had no real issues with the 4 blade from a performance stand point until I plotted prop slip through out my rpm range. What an eye opener.....

      Talked to a guy that props a lot of offshore boats. Suggested I go back to a 3 blade of a very different design and size than before.

      Very happy with the decision. Keep the lower end. Raised the top end and picked up rough 10% mpg in the process.

      The 4 blade is now a spare...
      ....

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      • #4
        As already stated, depends on what you're looking for. Overall, one is not better than the other.

        I've run all sorts of different props under all sorts of different conditions. I had a boat shop and really wanted to feel and know how the differences felt on my own boat, so I could talk with at least a little first-hand knowledge.

        And that's another thing. A particular prop may be wonderful on one boat, but on a different hull, it'll be terrible.

        So, all anyone here can offer you is personal experience, and why any particular prop is good or bad for their application.

        So, with that all in mind, here's my results, on my boat.

        Mirage - HATED IT! it has great bow lift, which on MY boat is terrible. It made the hull 'slam' coming off the tops of waves, even little ones. The prop was trying so hard to hold the bow up, then by the time the boat was far enough through the wave and the mass overcame the lift, the hull just dropped like a stone, BANG into the water, time after time.. It was terrible. Now, after testing it on his boat, I sold that prop to a guy with the same length boat, with the same engine but a different hull, and he loved it.

        Laser II - Nice prop, not a lot of lift (bow or stern), quick out of the water, especially with the vent plugs pulled. If you use it for pulling skiers, WARN them you are using a vented prop! That prop gets the boat from idle to full plane in a blink!

        Black Max (3 blade ali. Bog 'stock') - not a bad prop, but being ali tends to distort with power, and lose grip in turns.

        Vengeance - Very nice prop. I can pull full-lock turns at 30 knots without any ventilation (air being pulled into the blades, some call it, incorrectly, 'cavitation')...

        Alpha 4 - 1 inch higher pitch pulling the same WOT RPM, but 3 knots slower.. Yeah, go figure! Love this prop, quite immune to seaweed fouling and loss of grip, which is why I like it.

        Offshore/Vensura/Revolution 4 - very much the same as the Alpha 4, but with SS goodness.

        Generally, more blades means each blade is smaller, and the rake angle is higher (more 'swept back') and that, for me, means less problems with picking up seaweed.

        As also said, once you decide you want a new prop, go to a prop shop that will allow you to 'try before you buy'. If one shop says no, just go to the next one. I know when I had my Merc dealership, we could let the head office know the styles and pitches and a couple of days later, a big box of props arrived. I'd call my customer and let him know he was in for a fun weekend. He'd bring all the props back, bar the one he wanted to keep, and pay me for it... I had many satisfied customers that way, and they all said the same thing "I didn't realise a prop could make such a difference!"....

        Chris.........
        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
        The world takes on a whole new perspective when viewed from 100’ below.
        1972 Bertram ‘Bahia Mar’ 20
        2006 Mercruiser 4.3MPI (0W617679) w/Alpha One Gen II (0W829301)
        (Original - 1972 '165' In-line 6. Previous - 1994 4.3LX)


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        • #5
          Can’t really add much to the above excellent advice, other than that there are 3 blades out there that are that good, they almost border into the ability of a 4 blade, without losing all the upsides of a 3 blade. The tempest plus comes to mind.
          4 blades in my opinion are now usually only required on extreme applications. Worth also knowing that they can behave very differently should you be thinking the usual rules apply with pitch and resulting rpm. That is if going from a set of numbers taken from a 3 blade to go to a 4 blade. All but aluminium 4 blades, usually have a much larger diameter.
          as far as the best of them go, I’m not aware of any better than the Rev 4...but they won’t be suited to all situations. They almost always need big power to turn them well.
          the wee mercury spitfire aluminium prop is decent enough and sticks to the usual diameter found on an equivalent 3 blade.

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          • #6
            My limited span of props and performance doesn't equal other commenters here which have supplied us with some great information. My comment is that having run my first ported prop, the original Laser back in 1989, I got the benefit of a shallow pitched 4 blade with the performance of a high pitched 3 blade, giving me the best of both worlds in one prop. As others have stated, you don't really know till you run it, and on ported props, those that have variable diameter plugs, you don't know how much relief you want or need till you experiment with different sizes.
            If you are new to boating or have a new boat, a knowledgeable friend could show you how to operate your boat and save you a lot of grief, maybe some money, and maybe your life.

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            • #7
              Which boat and motor model do you currently own ? Your prop dissatisfaction is due to ?

              Happy Boating


              Sea Rider 320, 380 Sibs, 450 Rib, 2 Strokes Tohatsu 5,18 & 30 HP Proud Smokers

              Comment


              • #8
                No dissatisfaction , just rampaged curiosity, 16' fiberglass center console deep v- 14° dead rise , 70 hp fourstroke engine
                Bring rain gear !

                Comment


                • #9
                  Originally posted by Prophammer View Post
                  No dissatisfaction , just rampaged curiosity, 16' fiberglass center console deep v- 14° dead rise , 70 hp fourstroke engine
                  I went through four props on my current boat, really like two of them, sold the rest. What prop and pitch are u running now ? A basic three blade black max type aluminum?

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                  • #10
                    Originally posted by Scott06 View Post
                    I went through four props on my current boat, really like two of them, sold the rest. What prop and pitch are u running now ? A basic three blade black max type aluminum?
                    I bought this 2002 Crestliner 1750 Fish Hawk and Merc 2 stroke 115 back in June 2019. To my dismay, after running through 4 new props was that the PO didn't have it over propped, the engine had some quirks that had to be worked out and I mistook the quirks for too much prop since it wasn't really telling me it had the flu. Getting them cleaned up I put the original prop back on and it ran just fine.
                    If you are new to boating or have a new boat, a knowledgeable friend could show you how to operate your boat and save you a lot of grief, maybe some money, and maybe your life.

                    Comment


                    • #11
                      Originally posted by Prophammer View Post
                      No dissatisfaction , just rampaged curiosity, 16' fiberglass center console deep v- 14° dead rise , 70 hp fourstroke engine
                      To take the max out of that motor, some more tech info is needed, such as :

                      What's the boat's max passenger and HP rated for according to the tech plate if having one ?

                      What's the motor brand model ?

                      What's the max wot rpm achieved as usually loaded ?

                      What's the number of blades and current prop pitch in use ?

                      Happy Boating


                      Sea Rider 320, 380 Sibs, 450 Rib, 2 Strokes Tohatsu 5,18 & 30 HP Proud Smokers

                      Comment


                      • #12
                        Originally posted by Texasmark View Post

                        I bought this 2002 Crestliner 1750 Fish Hawk and Merc 2 stroke 115 back in June 2019. To my dismay, after running through 4 new props was that the PO didn't have it over propped, the engine had some quirks that had to be worked out and I mistook the quirks for too much prop since it wasn't really telling me it had the flu. Getting them cleaned up I put the original prop back on and it ran just fine.
                        Also a good point make sure everything is up to snuff before tossing parts at it. In my case I had just repowered, so very thing was working ok. None of my trials were wasted, just further honing in and lowering slip %

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                        • #13
                          I have no dissatisfaction or performance issues just curious about propellers
                          Bring rain gear !

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                          • #14
                            Loaded down with extra weight, tubing &/or in the weeds with motor tilted slightly up, I prefer 4-blade. But general cruising on long distance tours with 3 people, I like to use 3-blade. This works for me.

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                            • #15
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                              Originally posted by batman99 View Post
                              Loaded down with extra weight, tubing &/or in the weeds with motor tilted slightly up, I prefer 4-blade. But general cruising on long distance tours with 3 people, I like to use 3-blade. This works for me.
                              And there another secret... Don't try to buy a single prop to do everything, buy a couple of different ones that work for a particular task. And if you use the boat to pull skiers and tubers, buy one that is a couple of inches 'shorter' (less pitch), your engine and drive will thank you. And the boat will perform a ton better.

                              Like Batman99, I prop to the expected conditions and task. If I'm local, heading out for a dive, or close in fish, the 4 blade goes on, for its weed-shedding properties. If I'm heading way out, or up to the Abrolhos Islands and want the better efficiency, the 3 blade Vengeance goes on... I'll put up with a couple of stops along the way to clear the weed...

                              Chris.......
                              xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
                              The world takes on a whole new perspective when viewed from 100’ below.
                              1972 Bertram ‘Bahia Mar’ 20
                              2006 Mercruiser 4.3MPI (0W617679) w/Alpha One Gen II (0W829301)
                              (Original - 1972 '165' In-line 6. Previous - 1994 4.3LX)


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