Prop selection advise...

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  • Prop selection advise...

    Our boat is a 1994 sea ray 240 bowrider. 7.4 bravo 1 (330), engine serial # says its a Magnum but looks like a 330 to me. We've only had it for almost a year now. Its been a great boat, runs great!! Prop that came with it, Unknown because numbers are ground out of it, wasn't in the best of shape so we got a new one. Turning point 3-blade, SS, Express Mach 3, 14.25x21. Boat would rpm to 4900-5000 WOT at 48-49 mph. Target rpm is 4400-4800. So I tried a turning point 4-blade, SS, Express, 14x23, this time the best I could get was 4400-4500 WOT and 50-51 mph. Both times with average (typical 24 pack and snacks) load and around 1/2-3/4 of a 70 gallon tank of fuel. Boat specs at 4000 lbs dry but I think that's with the standard engine and drive, 5.7 alpha, so mine might be a bit heavier. The 4-blade prop feels good, boat rides nice and handles nice. plane time is slow to moderate but I chalk that to a heavy boat. 3-blade vibrates a bit, blows out in turns easy but planes quicker than the 4-blade, naturally from the lower pitch, still no leap frog tho. I notice the cavitation plate is buried on plane trimmed up just from the spray coming from drive area so I'm wondering if I should get a prop the lifts the stern a bit? We don't do any water sports, just cruise and occasionally stretch it out.
    Going from this, what prop would the more experienced than me recommend? We want a good cruising prop with top end in mind, we don't need a good hole shot.

    Oh...also, I think both the props we have, have a high slip ratio?

    Thanks everyone!!!

  • #2
    Yeah, that slip ratio is pretty high, and I'd also be curious, are you getting speed from GPS or speedometer?
    If its speedo, you might find its slipping even more.

    Getting a decent prop that hooks up stronger, would allow you to run a lower pitch.
    The lower pitch would give you much stronger acceleration and throttle response, and still keep your top end up.

    I would like to see what a Revolution 4 17 pitch would do on that setup.

    Are you still running, or is it cold and you have the boat put away?

    Is that speed from GPS or Speedo ?

    Ken Reeves
    KR@Propgods.com
    941-735-5808

    Comment


    • #3
      Yep...it's cold here, just got another 2" of white death today. Cincinnati ohio are.

      Yes, speed was confirmed on GPS phone app. Those speeds are the "Bests" I've seen with each prop. The 4 blade we have, I could only get 4200 rpm when I first installed it, cleaned and waxed the bottom and got another 200-300 rpm.
      The Rev 4? I looked at it a little but in my head I just can't decide on pitch because I'm not knowing how it will bite, slip, compared to the 2 props we have now.

      Anyone have experience with turning point props? What is your slip ratio?

      Comment


      • #4
        Originally posted by ken2 View Post
        Yeah, that slip ratio is pretty high, and I'd also be curious, are you getting speed from GPS or speedometer?
        If its speedo, you might find its slipping even more.

        Getting a decent prop that hooks up stronger, would allow you to run a lower pitch.
        The lower pitch would give you much stronger acceleration and throttle response, and still keep your top end up.

        I would like to see what a Revolution 4 17 pitch would do on that setup.

        Are you still running, or is it cold and you have the boat put away?

        Is that speed from GPS or Speedo ?

        Ken, how much slip do you think the rev 4 would have with my setup? Not going to quote your prediction, I just know you have better experience with that prop. The turning point props claim low slip but it wasn't true for my setup. Do you think the 14" diameter on that 23 pitch 4-blade may be why? The 3-blade we have (14.25x21) had a lower slip ratio but it was still to high.

        Comment


        • #5
          I would expect a Revolution 4 to be around 10-12% slip on your hull.
          If you could turn it up around 4900-5000 RPM, you'd still be getting 47-49 MPH at wide open. and acceleration should be a huge improvement.

          The Quicksilver Q4 is the exact same prop but 100 cheaper.
          Rev 4 cost $549 includes hub.
          Q4 cost $449 (you could use your turning point hub)

          I don't think the diameter was the issue with your turning point props, Probably just blade design and cupping.
          Could probably modify them a bit and make them hook up strong, but if you did, your RPM would drop a huge amount, so I'd just get a decent prop with a lower pitch.

          Ken Reeves
          KR@Propgods.com
          941-735-5808

          Comment


          • #6
            Originally posted by ken2 View Post
            I would expect a Revolution 4 to be around 10-12% slip on your hull.
            If you could turn it up around 4900-5000 RPM, you'd still be getting 47-49 MPH at wide open. and acceleration should be a huge improvement.

            The Quicksilver Q4 is the exact same prop but 100 cheaper.
            Rev 4 cost $549 includes hub.
            Q4 cost $449 (you could use your turning point hub)

            I don't think the diameter was the issue with your turning point props, Probably just blade design and cupping.
            Could probably modify them a bit and make them hook up strong, but if you did, your RPM would drop a huge amount, so I'd just get a decent prop with a lower pitch.
            Thanks for the advise ken. Currently I have the boat off the trailer converting to bunks from a roller trailer then fixing some scrapes in the keel from previous owner beaching it. After that the bottom is getting a full wet sand with 1500-2000 grit then buffed to a shine again with good sealer/wax. That may change my numbers a bit so I'll get back with you in the spring with updated numbers at wot and cruise speeds and see what might work best. I gave my 4 blade prop to a buddy of mine for Christmas but I'll still be able to try it and see what difference it makes vs the 3 blade I have.

            Comment


            • #7
              Sounds good, let us know how it goes.

              Ken Reeves
              KR@Propgods.com
              941-735-5808

              Comment


              • #8
                Ok Ken. It's been a while since we were able to get the boat out but was finally able to yesterday.

                we had the turning point 3 blade 21 pitch prop on it. Packed full of fuel (coming out of vent, 70 gallon tank) sea level, 4 adults and cooler drinks. Boat would run 51 mph ( verified with phone GPS app) at about 4650 rpm. So with the load it had it was getting to its high end of rpm range. When the water got a little rough with head wind it hit 48 mph at a bit more slip, 4850 rpm.

                I sure don't like the feel of the 3 blade I'm running right now. It's not as smooth, feels like it vibrates easy. The old 4 blade I had was silky smooth.

                Here is what has changed on boat to make the numbers different from my first post. Bottom of boat had all gelcoat scrapes and gouges repaired (looks new on bottom now 😁) with full polish and seal of bottom.
                Drive unit removed (paint very rough and corrosion pitted), paint stripped and pitting filled and smoothed and chunk out of skeg repaired. Other than quality of paint used the drive looks great now. 😁

                So I suppose the bottom refinish and drive finish made the boat more effecient.

                What prop do you think is right for it now? No skiing or tubing. We just cruise and park.

                Comment


                • #9
                  If it was cold outside, that will also give you a couple mph and more RPM. makes a surprising difference.

                  Close call between the 17 or 19.
                  17 will have great acceleration but top out at 47-49 MPH.
                  19 will have decent acceleration and should be able to crack 50

                  The Quicksilver Q4 would still be the prop I'd go with.
                  no tubing, just cruising, the 19 would be my choice.

                  Ken Reeves
                  KR@Propgods.com
                  941-735-5808

                  Comment


                  • #10
                    Air temp was 82 that day. Water temp ??? Not so sure but it was cold. Way to cold to get in still. Lol

                    Comment


                    • #11
                      If it was 82, then your good. Go with a 19.

                      when its 40-50 degrees outside they do run stronger, but 82 is fine.

                      Ken Reeves
                      KR@Propgods.com
                      941-735-5808

                      Comment

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