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    Contessa cb prop

    Hey all

    i have a 86 contessa 5.7. I have alot of weight on back end (battery’s ). I had a aluminium 16(dia) x 15 pitch 3 blade. she would due about 20 knotts at 4300 -4400 rpm but wouldnt get her stern out to plane. I was advised if i went to a 4 blade and stainless i would get a bit more “punch” and it probably make her plane but might lose a few knotts top end. I got ahold of a brand new solas saturn 4 blade 15.5(dia) x 15 pitch. I only tried it once so far and all she do was 8.4 knotts dont know about rpm. I will check when i try again tomorrow. What i cant understand is why the stainless 4 blade is so much slower at the same pitch. Any ideas.. of

    #2
    I don’t even know if it’s possible but the only thing that comes to mind is could the prop be mounted backwards?
    Drew Haas
    1998 4788 "Painkiller"

    Comment


      #3
      The 16x15 was rh and the 15.5x15 is left hand ( or other way around) but bin told from many many people the 280 can run eather way. Unless anyone here knows better ???

      Comment


        #4
        Originally posted by Andrew fraser View Post
        The 16x15 was rh and the 15.5x15 is left hand ( or other way around) but bin told from many many people the 280 can run eather way. Unless anyone here knows better ???
        the 270/280 can be ran either way. one only has to pull the cover off the drive and switch the linkage rod to the other end of the shift lever so the helm control throw is in the correct direction.

        a 4 blade prop grabs more water..... a number of things here. you either need more slip, which is partially controlled by diameter and partially controlled by the individual blade surface area (and number of blades), or less pitch... a fat bladed prop has less slip, and a skinny bladed one has a lot of slip, but this depends on how much power is applied to it.
        the design of a prop is a very dynamic thing and any slight change in design or applied power will change its characteristics across the board...

        its been said by many that a fat bladed prop with the correct pitch is better than a standard size prop. and in my experience, a 4 bladed prop is an expense that is only reasonable when one has excess power that needs to be used.... the contessa with a 5.7 doesnt qualify as a boat with excess power.

        the 5.7 engine should run at its recommended 4600rpm, and on a heavy boat, maybe a few extra rpm wouldnt hurt... BUT, not to be ran there all the time, but just be able to make the rpm so when at cruise rpm range, the engine is running without laboring on the torque curve......

        personally, I firmly believe the trim tabs installed are too small for the boat, I installed the larger 12x24 tabs on mine and it made a huge difference... the OEM sized tabs need to be used in conjunction with the trim of the outdrive to get the attitude of the boat correct, and too much or too little of one or the other will cause the engine to labor, not climb fully on plane, and not make the rpm necessary to insure its running easily within its torque curve..


        NU LIBERTE'
        Salem, OR

        1989 Bayliner 2556 Convertible
        5.7 OMC Cobra - 15.5x11 prop
        N2K equipped throughout..
        2014 Ram 3500 crew cab, 6.7 Cummins
        2007 M-3705 SLC weekend warrior, 5th wheel
        '04 Polaris Sportsman 700 -- '05 Polaris Sportsman 500 HO
        Heavy Equipment Repair and Specialty Welding

        Comment


          #5
          Originally posted by Andrew fraser View Post
          Hey all

          i have a 86 contessa 5.7. I have alot of weight on back end (battery’s ). I had a aluminium 16(dia) x 15 pitch 3 blade. she would due about 20 knotts at 4300 -4400 rpm but wouldnt get her stern out to plane. I was advised if i went to a 4 blade and stainless i would get a bit more “punch” and it probably make her plane but might lose a few knotts top end. I got ahold of a brand new solas saturn 4 blade 15.5(dia) x 15 pitch. I only tried it once so far and all she do was 8.4 knotts dont know about rpm. I will check when i try again tomorrow. What i cant understand is why the stainless 4 blade is so much slower at the same pitch. Any ideas.. of
          The SS prop has more drag from the extra blade and is heavier than the aluminum so the pitch should have been reduced, since you stayed the same pitch your performance will decrease as you experienced.
          1997 Maxum 2400 SCR 5.7LX Bravo II

          Mike

          Comment


            #6
            Hey all

            i had it out again and it did mid teens. Not sure how much tidal flow there was. I think 3 ish knotts. Wot was 3800. I contacted the prop place they said its the smallest pitch they sell/ make but they could reprofile the prop a pitch or two lower. Is it worth it? Does it work? And downsides like weaker prop etc? Or do i go back to a alumimum prop and lower pitch ?

            Comment


              #7
              Originally posted by Andrew fraser View Post
              Hey all

              i had it out again and it did mid teens. Not sure how much tidal flow there was. I think 3 ish knotts. Wot was 3800. I contacted the prop place they said its the smallest pitch they sell/ make but they could reprofile the prop a pitch or two lower. Is it worth it? Does it work? And downsides like weaker prop etc? Or do i go back to a alumimum prop and lower pitch ?
              its a lot cheaper to have the prop profiled than it is to buy a new one again.... 3800rpm is not nearly enough, and it may take 2-3 inches of pitch change to get where you should be... the problem is, they problably cant make that much change in the prop..

              personally, I am a fan of the less expensive aluminum props for most applications on these type of boats... when one is looking for ultimate high speed performance, then stainless becomes a good option, but the 28 will need a much larger and more powerful engine before one will see a difference in performance in stainless over a properly sized aluminum prop....


              NU LIBERTE'
              Salem, OR

              1989 Bayliner 2556 Convertible
              5.7 OMC Cobra - 15.5x11 prop
              N2K equipped throughout..
              2014 Ram 3500 crew cab, 6.7 Cummins
              2007 M-3705 SLC weekend warrior, 5th wheel
              '04 Polaris Sportsman 700 -- '05 Polaris Sportsman 500 HO
              Heavy Equipment Repair and Specialty Welding

              Comment


              • Nauti_Mike
                Nauti_Mike commented
                Editing a comment
                Agree.

              #8
              16 x16 or 15 elephant ear OEM or Michigan wheel oem replacement are the optimal prop with this combo, assuming your engine is good. It should do 25-28 mph with this combo. Larger tabs in the 18-24 inch drop tab configuration and wedge the tabs so the line up with the warter flow, and you can do 32-35 WOT at 44-4600 rpm.

              If you were doing 20 knots you were on plane. This boat will plane out at 16 or so.
              1986 Bayliner Contessa 2850
              In over my head for sure!!
              M/V SKUA refit
              https://www.baylinerownersclub.org/f...ak-gctid499442

              https://www.baylinerownersclub.org/f...contessa-refit

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