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Mako 252: which propellers ?

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  • Mako 252: which propellers ?

    Dear friends,

    I recently purchased a 2000 Mako 252 with twin Evinrude 175 ficht in perfect conditions (It was a very good deal!) and I am sure that the propellers selected by the previous owner are not right.

    It mounts a couple of 4 blades SS Renegade 14.5x19" and here follows the behaviour of the boat.

    With calm water at full trottle the engines reach 5000rpm instead of 5400-5600 as it should be. Maximal speed is around 39knots.

    With rought water I am obliged to tilt down very much the engines otherwise I have cavitation problems. Cruising with engines tilted down makes the bow too heavy.

    Generally my feeling is that the pitch is too long and that the bow is too "heavy".

    I have no experience with 4 blades propellers therefore I don't know the difference in performance against 3 blades.

    It would be great to have the opinion of someone with more experience or eventually with the same boat to start testing a new pair of propellers according to his suggestion.

    Regards,

    Paolo (Rome, ITALY)
    2000 Mako 252, twin 175 ficht + 15 4 strokes kicker - Rome ITALY

  • #2
    come on...

    No answers?

    Please squize your brains I need your help!
    2000 Mako 252, twin 175 ficht + 15 4 strokes kicker - Rome ITALY

    Comment


    • #3
      I would see if you could borrow a set of 14.25 x 19 x 3 blades to get the RPM up. If those get you into the +/-5500rpm range, try those for a while. My 25'er had twin 175hp 1999 Johnsons before the 200hp Rudes and 15x21x3 was the best for me then. IMO 4 bladed props are for real heavy boats with "recommended" mid range power. They help on whole shot and keeping on plane with less stress on the foot, especially with a heavy load.
      Artie Sutherland[br]Rude Attitude -\'76 Mako 25 CC. - SOLD[br]1976 Mako 21[br]2002 Yellowfin 31 - 300 hp Suzukis[br]Gulf Coast, Mississippi[br]

      Comment


      • #4
        Thank you for your prompt reply!

        I will try with 3 blades and same pitch.

        Do you know if 4 blades propellers pull up the stern? I have been told that and it is also my impression.

        I would like to keep the bow lighter than it is now.

        Regards,

        Paolo
        2000 Mako 252, twin 175 ficht + 15 4 strokes kicker - Rome ITALY

        Comment


        • #5
          quote:


          Originally posted by Paolo


          ...... Do you know if 4 blades propellers pull up the stern? .....



          Ummmmmmmmm ...... errrrrrrrr...... hmmmmmmmmm .... ahhhhhhhh..... [88][88]

          That's Mississippi English for "no clue". [:x)][(#)] I have heard 3 vs 4 blades can affect how the bow rides, but no personal expereince (key word being "heard"). I think Ring tried both on a single engine 21' and may have a comment, but he's busy cleaning teeth and painting the chair railing and steps for his boat (??) [:x)][]....
          Artie Sutherland[br]Rude Attitude -\'76 Mako 25 CC. - SOLD[br]1976 Mako 21[br]2002 Yellowfin 31 - 300 hp Suzukis[br]Gulf Coast, Mississippi[br]

          Comment


          • #6
            If you get it propped correctly (5600 rpms) the extra speed "May" help with the heavy bow but that will need to be tried. Also, are the motors cavation plates right at the boat bottom where they are susposed to be? Is there any way you could move some of the weight (anchors etc) that is in the bow back closer to admidships (CC area)? Where are your batteries located? Could you move them to trim the load? Do you have a gas tank that is up forward of the CC? If so try running with that tank MT or using it first when you go out. Just some thoughts -

            Mike
            1973 22 CC Milford, CT USA[br]

            Comment


            • #7
              Dear Mike,

              thanks for you comments.

              Today I was thinking about another possibility that you also suspect because of your question regarding the cavitation plates.

              Maybe the engines are mounted a little bit too high (just an hole) and, in order to avoid cavitation, I am obliged to tilt down the engines creating a disadvantageous angle between props and hull.

              This could generate the "heavy bow" and reduce performance.

              If this is the reason maybe props are OK.

              Unfortunately the boat is in the water and I have no good pictures from the back to confirm or exclude this option.

              Anyway, this is my strong feeling.

              Regarding weight distribution everything is standard and nothing very heavy is in the bow storage compartments.

              Could a too long pitch generate cavitation problems?

              Ciao,

              Paolo (Rome, Italy)
              2000 Mako 252, twin 175 ficht + 15 4 strokes kicker - Rome ITALY

              Comment


              • #8
                Paolo - Usually if the diameter of the prop stays the same, the higher the number of the pitch will create cavation - but with that statement you need to remember the number of the pitch is relative. Most boats like Makos will run a 17 or a 19 pitch with no problems - the heaver boats requiring the 15 , 17 (or 19) for more power to get on plane and keep the heaver load running along on top of the water at the max RPMS. Some of the lighter boats (like my '73 22) can go to a 21 or a 23 pitched prop with no problems - giving more distance per revoulation of the prop - faster and more miles per gal but they do experience cavation in some situations like following seas or on hard hole shots. Again your pushing a lighter load onto plane and requiring less power to keep it there at speed. The other thing is to have the motor rev up to where it is making max HP - idealy in that 5400 to 5600 rpm range. Ideally want you want is to have a prop that will give a good hole shot (or at least one you can live with) good mid range power and a maxed out RPM's at WOT - but also not have cavation with following seas or any other time. If your RPMs are not maxed out at wide open throttle (WOT) then your pitch is usually low maybe by 1 or 2 pitches. (Incendently props can be changed by 1 pitch if necessary by a shop that reconditions props, but you need to specify what you want. I would also recommend SS props as they have thinner cupped blades which deliver more power to the water.) I have run several different (AL and SS) 3 bladed props on all my motors but do not have any experience with 4 blades - but do know that they are usually used for heaver boats that need to get on plane sooner and are usually pitched lower (17, 15, 13 pitch). If I were you, I would pull the boat (or jump into the water) and take a close look at those cavation plates. Also - another reason that you could be slow and have draging problems is excessive marine groth on the bow of the boat so check that out while you in the water. Another thought - Maybe the motors are mounted on a little closer together that they should be which would place the (never know what people do ??) cav plates off the smooth stream of water coming off the underside of the hull. Just some thoughts -

                Mike
                1973 22 CC Milford, CT USA[br]

                Comment


                • #9
                  Dear Mike,

                  thanks for your response. I give some more info.

                  Hull very clean.

                  SS props.

                  Cannot practically work with T-tabs. As son as I touch them bow becomes extremely too heavy. If the only problem were prop pitch, how could you explain that?

                  Do you consider Mako 252 an heavy boat for 350Hp?

                  I really would like to solve the problem because everything else is just perfect. I am coming from many years of Boston Whaler Outrage series and I would like to love Mako as much as I did BW.

                  The problem is that previous owner did not know anything about boating. Immagine that when I purchased the boat I found instruction sheets inside rof holders!

                  You may consider this boat as just coming out from the dealer the vey first day without being tested in the water.

                  Ciao,

                  Paolo
                  2000 Mako 252, twin 175 ficht + 15 4 strokes kicker - Rome ITALY

                  Comment


                  • #10
                    Years ago a friend of mine had, I think an 1984 or '85 25 foot Mako w/ twin 185's on her. She would run close to 65 MPH on a flat sea and the bow was not at all heavy when under way. Can't remember if he had tabs though? Anyways with the added information about the trim tabs - I would take a closer look at how they are mounted and wether or not they can be retracted (up) enough - because the symptom your are describing is exactly the way the boat would run with the tabs down way to far thus lifting the stern of the boat up more that normal. Do the tabs have an auto retract on them (electronics that automatically retract the tabs once the engines are turned off or the key is turned on?? Could the tabs be wired backwards causing the tabs to go all the way down when you touch them instead of moving up or down by your command from the helm? Hope this gives you some new ideas -

                    Mike
                    1973 22 CC Milford, CT USA[br]

                    Comment


                    • #11
                      4 blade props will reduce rpm by approximately 100RPM from a similarly pitched 3 blade.

                      4 blade props accelerate better and hold better at low to mid speed which make them better for rough conditions.
                      [br]***[br]\'82 Ski Nautique - Lake Martin, AL[br]\'80 236IB - Lake Martin, AL[br]\'03 Pursuit 2670 - Destin, FL

                      Comment


                      • #12
                        next week end I'll do more test and ? will take a look at the default position of trim tabs.

                        I'll let you, thanks again,

                        Paolo
                        2000 Mako 252, twin 175 ficht + 15 4 strokes kicker - Rome ITALY

                        Comment


                        • #13
                          Sounds good - Let us know how you make out.

                          Mike
                          1973 22 CC Milford, CT USA[br]

                          Comment


                          • #14
                            Paolo-

                            You're heavy bow is not a function of 3 vs 4 blades, it is more a function of the rake of the blades on the props. Rake is how the blades are 'angled back'. More rake = more bow lift.

                            A four blade wheel, from what I've seen anyways, will rob you a bit of top end, run about neutral in the midrange, but give you better planing and holeshot on the low end.

                            A 4 bladed wheel should stay hooked up much better than any three blade wheel. If you're having cavitation issues, your engines are probably mounted too high.

                            I would first try and drop the engines a hole. Then see where you're at. If you stay hooked up and can run with trim, thus getting the bow up, then start adressing the RPM (pitch)issues. If you cant keep 4 bladers hooked up, those engines must be high, and its only going to get worse if you throw three bladed wheels on them.
                            1990 261 T/2001 200 HPDIs[br]Basking Ridge/Mantoloking NJ[br]

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                            • #15
                              Dear Makorider,

                              thanks a lot for your comment. In the last couple of days thinking about the performance of the boat I also came out with the same conslusion and I am very happy that someone else suspects the same.

                              I have the feeling that the engines are just mounted too high, therefore I am obliged to trim down them and the angle is bad.

                              I have just an hole left on top but I am not sure if the engines will touch the stern. I'll check next week-end.

                              Which model do you own?
                              2000 Mako 252, twin 175 ficht + 15 4 strokes kicker - Rome ITALY

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