Announcement

Collapse
No announcement yet.

Owners listing 2858, 2859 and 289

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    Prop woos so on Fry the S&W got wet once more, earlier try with 4 blade prop 20P was bad under propped , so the exchange was made, so new installed 4 blade 24P still under propped, better but still cant get on top no bite RPM going up to red line and can go past, red line at 3600RPM. Question 1 are there props for the Bravo III with larger Dia. 2 how high a pitch can you go?
    Slightly modified 2859 6.5 Diesel Bravo III X drive
    96 Dodge 5.9 5 speed Gear vender OD.

    Comment


      Since switching to a Bravo III on the positive side, the slow speed wandering is one.
      Slightly modified 2859 6.5 Diesel Bravo III X drive
      96 Dodge 5.9 5 speed Gear vender OD.

      Comment


        I think your drive ratio needs to be looked at. I’m no expert but you installed an engine with much more torque than your 7.4. I’d think the ratio should have went down numerically from where it was idk??
        Dave
        Edmonds, WA
        "THE FIX"
        '93 2556 5.7 Bravo II 2.0:1 18 1/4x19 P
        (.030 over-Vortec top end-part closed cooled)
        The rebuild of my 2556 https://www.baylinerownersclub.org/f...76?view=thread
        Misc. projects thread
        https://www.baylinerownersclub.org/f...56-gctid789773

        Comment


          Hi Dave the drive was changed to Bravo IIIX ratio,--Ratio by ENG. builder, recommendation to 220, so that is what I have, yes it may need to go to 2.00 don't know jet. My next move is send them in for exchange, pulled them of and Monday there of to HILL marine for a set of 28P I am thinking. P/N my old Eng. was a 350 260HP. Have not had the Drive apart what gears would need changing? I
          Slightly modified 2859 6.5 Diesel Bravo III X drive
          96 Dodge 5.9 5 speed Gear vender OD.

          Comment


            I’m no expert on picking the correct drive ratio. What I know is say you run a sbc in a boat like mine. The sbc would normally be marginal at best but with the Bravo drive 2.0:1 (in my case) ratio it works really well. Now if I change my sbc for a bbc with more torque I would most likely need to reduce the drive ratio to a 1.89:1 (or whatever) because the bbc provides quite a bit more torque than the sbc did and would simply over rev to some degree as yours is doing. My guess is your new diesel power plant produces an excessive amount of torque compared to your or my sbc and it seems odd that someone would recommend a 2.20:1 ratio not to mention the added thrust from it having counter rotating props.
            Someone like Rick could confirm or de bunk my theory
            😆
            regardless of all that I hope you get her up on a happy plane soon and I’m still waiting for your “shake down with new power package” you tube video...
            😁
            Dave
            Edmonds, WA
            "THE FIX"
            '93 2556 5.7 Bravo II 2.0:1 18 1/4x19 P
            (.030 over-Vortec top end-part closed cooled)
            The rebuild of my 2556 https://www.baylinerownersclub.org/f...76?view=thread
            Misc. projects thread
            https://www.baylinerownersclub.org/f...56-gctid789773

            Comment


              Thanks Dave, Perhaps Rick will see this.
              Slightly modified 2859 6.5 Diesel Bravo III X drive
              96 Dodge 5.9 5 speed Gear vender OD.

              Comment


                Dave sent me a PM linking me to this thread.
                I may have seen it had it been posted in the Tech Section forum!


                Hi Dave the drive was changed to Bravo IIIX ratio,--Ratio by ENG. builder, recommendation to 220, so that is what I have, yes it may need to go to 2.00 don't know jet. My next move is send them in for exchange, pulled them of and Monday there of to HILL marine for a set of 28P I am thinking. P/N my old Eng. was a 350 260HP. Have not had the Drive apart what gears would need changing? I
                With what I have learned over the years, when changing from a higher RPM engine to a more torque oriented engine (with less RPM capability), the propeller must be spun at a higher revolution.

                But I digress for the moment.

                When you refer to 220, are you meaning a reduction of 2.20 : 1?
                In other words...... an engine rotation of 2.2 to a propeller rotation of 1?
                If so, a reduction of 2.20 : 1 would typically be used for a low torque but high RPM engine.

                Since I am not familiar with the different BIII ratios, I can only give you a few examples using Volvo Penta:

                BBC or BBF w/ Duo Prop...... the final reduction would be 1.78 : 1
                SBC or SBF w/ Duo Prop....... the final reduction would be 1.95 : 1
                Small high RPM engine w/ Duo Prop....... the final reduction would be 2.30 :1

                As you can see, the numeric value becomes higher as the torque is reduced.
                In other words, the reduction is greater as we go to a smaller/less torque producing engine.

                The small but high RPM engine needs the lower reduction in order to transfer the torque to the propeller.
                The smaller engine's higher RPM makes up the difference (of the greater reduction), by spinning the propeller faster once the boat is moving.


                I also know for certain, that we can never "prop" ourselves out of an incorrect drive reduction. It just doesn't work like that!


                If I'm understanding that your reduction is now 2.20 : 1, I would think that you need to go to a lessor reduction, and then drop down on prop pitch!

                Rick E. Gresham, Oregon
                2850 Bounty Sedan Flybridge model
                Twin 280 HP 5.7's w/ Closed Cooling
                Volvo Penta DuoProp Drives
                Kohler 4 CZ Gen Set

                Comment


                • builderdude
                  builderdude commented
                  Editing a comment
                  Thanks Rick👍

                Since this thread was started back in November of 2017, it may better serve you to start a new/fresh thread in either the Tech or Cruiser Section.
                Rick E. Gresham, Oregon
                2850 Bounty Sedan Flybridge model
                Twin 280 HP 5.7's w/ Closed Cooling
                Volvo Penta DuoProp Drives
                Kohler 4 CZ Gen Set

                Comment


                  Thank you Rick what you are indicating, is correct and I am thinking in P/U truck terms 411 V. 356 got that \, I have sent the 24 P props back, 28 P props on the way if that is not satisfactory, drive gears will need to change, perhaps to a 2.00. The thing that bugs me that ratio was recommend by the ENG. builder. Yes I should have gone to Tech. Thank you once more for your great input.
                  Slightly modified 2859 6.5 Diesel Bravo III X drive
                  96 Dodge 5.9 5 speed Gear vender OD.

                  Comment


                    Originally posted by 2850Bounty View Post
                    Since this thread was started back in November of 2017, it may better serve you to start a new/fresh thread in either the Tech or Cruiser Section.
                    He did have s separate thread going at one point but me thinks it vanished when we had a BOC swap.

                    Fritz, I think it’d be a good area to start another thread and post in tech. Include the torque/rpm values for your new engine
                    😁
                    Dave
                    Edmonds, WA
                    "THE FIX"
                    '93 2556 5.7 Bravo II 2.0:1 18 1/4x19 P
                    (.030 over-Vortec top end-part closed cooled)
                    The rebuild of my 2556 https://www.baylinerownersclub.org/f...76?view=thread
                    Misc. projects thread
                    https://www.baylinerownersclub.org/f...56-gctid789773

                    Comment

                    Working...
                    X