Prop help: 2001 Cape Horn 24 Twin F150’s

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  • Prop help: 2001 Cape Horn 24 Twin F150’s

    Just placed a deposit on a new to me boat today. Been reading up quite a bit and it seems like a prop change may be in order.

    Boat currently has the engine the whole way down (top mounting hole), current props are unknown, and saw cruise at 4100 rpm @30 mph with light load. And WOT 5400 rpm at 45mph. Speeds and RPM based off Yamaha round gauges.

    My first check will be to raise the engines up to the highest position (bottom hole) based on others feedback on THT for this boat, and I was unable to see the cav plate at cruise. The boat did suffer slightly from porpoising, and I’ve been told that a Rev 4 17P helps this out, but will the 4 blade negatively affect RPM, and top speed?

    I feel like this should be a 6,000 rpm 48mph boat when tuned right with the F150’s.

    looking for prop recommendations from the PROPGOD

  • #2
    most guys I see are in the mid 40's realistically. (just like you)
    I've seen some claim faster, and they might get it, but don't know if they are hopping up and down when they get those speeds or not.

    I'd want to try either Rubex HR4's (I have a set we could test)
    and I've also had good luck with Powertech SCE4's, they give a lot of sternlift, and should do very well.
    Either one I'd go 17 pitch.
    I don't think you'll loose speed, but I don't think your going to gain any either, its just going to ride better.

    The Powertech's take about 6 weeks to get.
    The Rubex, I can get in a couple days.
    Just give me a call.

    Ken Reeves
    [email protected]
    941-735-5808

    Comment


    • #3
      Originally posted by ken2 View Post
      most guys I see are in the mid 40's realistically. (just like you)
      I've seen some claim faster, and they might get it, but don't know if they are hopping up and down when they get those speeds or not.

      I'd want to try either Rubex HR4's (I have a set we could test)
      and I've also had good luck with Powertech SCE4's, they give a lot of sternlift, and should do very well.
      Either one I'd go 17 pitch.
      I don't think you'll loose speed, but I don't think your going to gain any either, its just going to ride better.

      The Powertech's take about 6 weeks to get.
      The Rubex, I can get in a couple days.
      Just give me a call.

      Ken,

      Would you agree also with raising the engines up to get closer to 6,000 RPM’s before I start swapping props? Or start with a 4 blade prop in the current height.

      Comment


      • #4
        Well I don't know what your current propellers are.
        your risk is if you raise the motors and the current props ventilate because they don't have enough traction, then your not really able to use your boat till you get new props.
        or you end up moving the motors a lot.

        Ken Reeves
        [email protected]
        941-735-5808

        Comment


        • #5
          Originally posted by ken2 View Post
          Well I don't know what your current propellers are.
          your risk is if you raise the motors and the current props ventilate because they don't have enough traction, then your not really able to use your boat till you get new props.
          or you end up moving the motors a lot.
          Sorry bout that, never updated the post after I picked the boat up. Yamaha Reliance 19P 13.75”

          Comment


          • #6
            They are not bad props, but they may not be able to keep traction at the higher height.
            how does the boat run so far, did you get to go out yet ?

            Ken Reeves
            [email protected]
            941-735-5808

            Comment


            • #7
              Originally posted by ken2 View Post
              how does the boat run so far, did you get to go out yet ?
              Runs ok, has a slight porpoise at cruise, still averaging 45 mph 5400 rpm WOT, with cruise at 30mph 4100 rpm. but the previous owner remounted the trim tab actuators 1.5” lower on the transom effectively keep the tabs always engaged ( can only assume this was to combat porpoising) I was going to raise the tabs back up to oem position, gauge porpoising from there before I start adjusting props / engine height.

              All theoretical, but perma-tab as I’m referring to them are hurting my speed but helping porpoising, the engine height is hurting RPM, and increasing porpoising. Seems like I should take it all back to a fresh start before I start adjusting.

              Comment


              • #8
                Yes, I agree.

                So, you'd have to remount the tabs back up where they should be. Then you are likely going to notice the porpoising.
                raising the motors and going to 4 blades will help make the boat ride better and improve your fuel burn.


                Ken Reeves
                [email protected]
                941-735-5808

                Comment


                • #9
                  Thanks Ken,

                  I’ll report back with findings once I correct those items.

                  Comment


                  • #10
                    Originally posted by ken2 View Post
                    Yes, I agree.

                    So, you'd have to remount the tabs back up where they should be. Then you are likely going to notice the porpoising.
                    raising the motors and going to 4 blades will help make the boat ride better and improve your fuel burn.
                    Ken,

                    Long delay as I spent the last 4 months rewiring and refitting the boat over the winter. Finally got her in the water and have some updated numbers, curious to your recommendations on props.

                    I raised the motors up to the bottom mounting hole (all the way up) and am still running Yamaha SWS 19 pitch props 13.75 diameter and changed my tabs back to factory location.

                    Cruise at
                    3500 rpms
                    30-31mph
                    2.4mpg

                    WOT
                    5700 rpms
                    48mph
                    1.8 mpg

                    no prop blowout in turns, no sounds of ventilation on a following sea, and still pops out of the hole pretty quick, but falls off plane a bit too soon (low 20's). porposing has all but gone away on slick calm water, but add some chop, or deacceleration and i have to add a lot of tab to get the bow back under control.

                    Comment


                    • LFBB
                      LFBB commented
                      Editing a comment
                      Is this a light load or geared out with ice, 3 guys and beer? Falling off plane in the 20's is my biggest worry, I'd much rather see the high teens. When tabbed all the way what is the lowest speed you can remain on plane?

                  • #11
                    Well, it doesn't' sound bad at all.

                    but if you want a little more ability to put that bow down, the HR4's or SCE4's would be the ones to try.

                    Ken Reeves
                    [email protected]
                    941-735-5808

                    Comment


                    • #12
                      Originally posted by ken2 View Post
                      Well, it doesn't' sound bad at all.

                      but if you want a little more ability to put that bow down, the HR4's or SCE4's would be the ones to try.
                      LFBBThis was a light load heading out to the islands for a sandbar day. Full tank of Fuel (215 gallons) and a cooler of beverages. no ice in the fish box, no tackle or gear. I should have specified that.... I'd imagine my numbers will be much lower on all fronts once I add two more anglers, and gear.

                      ken2 my hesitation with dropping to a 17P 4 blade is the loss of speed, running the Herring Prop Calculator at 6% slip which I seem to be getting currently has me at WOT of only 45ish MPH. is that a good comparison though? 6% slip even with the 4 blade?

                      Comment


                      • #13

                        I don't think 4 blades are going to be faster, good chance you would loose a couple MPH.
                        but you might like the ride better.
                        yes you might only get 45 MPH

                        Ken Reeves
                        [email protected]
                        941-735-5808

                        Comment

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