31' Fountain, twin Merc V8 300's - room for improvement?

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  • 31' Fountain, twin Merc V8 300's - room for improvement?

    Hello, I have a "95 Fountain Sport CC,with new (50 Hrs) twin Merc 300 V8's. Just straight 4 stroke, not the R , not the Verado. CMS midsection.
    Here is my setup. Wondering if there is any room for improvement in efficiency or top end?
    No bottom paint, has radar arch, no radar.
    Running Bravo1 22p 4 blade in near perfect condition.
    Trimmed up.


    Numbers with engines mounted in 4th hole, (almost all the way up).
    RPM MPH MPG SLIP
    3000 30 2.5 16
    3500 37 2.4 11
    4000 42 2.2 11
    4500 51 2.0 5
    5000 55 1.7 7
    5500 62 1.4 5
    5950wot66 1.3 6

    I have raised the engines to the highest position (bottom hole) for a comparson.
    RPM MPH MPG SLIP
    3000 30 2.6 16
    3500 37 2.5 11
    4000 42 2.3 11
    4500 48 2.0 10
    5000 53 1.8 11
    5500 61 1.4 6
    6050wot 67/68
    1.3 5

    Some one suggested Bravo FS to lift the bow some. What do you think? Leave it or experiment?

    Thanks
    Bill

    Last edited by satbeachbill; 01-09-2020, 02:11 PM.

  • #2
    Ken should be along shortly.
    Unless I am wrong, traditionally four blades are slower. Let's see what Ken says.
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    • #3
      I’d guess you’re pretty darn close
      In testing the new 34’ w/ twin 350 VRod’s, when she was first introduced, we (Propbender & I) were 66-68mph with Rev4’s and Eco’s
      He’s astute enough to feel difference all the way through rpm range—me, only hole shot and top end.
      Ken may can dial you in a little tighter but Prop is the most experienced Fountain guru out there IMHO
      ’19 Invincible 36 - 350 Verado’s Sold
      ’20 Invincible 35’ Cat, Quad Merc V8’s
      Fairhope & Orange Beach, AL

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      • #4
        Yep, may very well be pretty close. And yes, I''ve followed Ken and Chris's (PropB) posts religiously.

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        • #5
          Chris "Propbender" is definitely a good guy to ask. He knows them well.
          as for your numbers, they are Very good ! if you gain anything, it will be very small.

          A lot of guys liked the original Bravo 1's on that hull, because the ride was great. it helped keep the bow down and was great in rough water.
          Back with the original size gearcases, the Mirage Plus was a couple MPH faster on top end, but didn't ride as well in rough water.
          With the new larger 5.44 diameter gearcases, the Enertia ECO would be an interesting one to try.
          Cruise economy would probably be a little better, top end would be very close.
          Bravo FS props give more bowlift, less sternlift, however you want to look at it. They might go 1 or 2 MPH faster, but thats about it.

          For economy, we could test some 22 ECO"s and see what it does.
          I don't have a LH/RH set of Bravo FS to try. I would expect 1 or 2 MPH faster basically. and you'd probably have to go to 24's because the slip is normally 15-20% on the FS.


          Ken Reeves
          [email protected]
          941-735-5808

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          • #6
            Thanks Ken. I thought the slip #'s here were pretty good as it is. I 'll keep investigating the FS.

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            • #7
              Ken,

              I talked with Chris,( propbender).
              He made a couple suggestions:
              1)
              Lower the engines back to the 4th hole: a) keeps in it off the rev limiter and b) by lowering the motor one hole, would have more control of bow lift with engine trim. ( I thought the bow had pretty good response from trim with either hole as it was.) Guess it could be improved.) I did notice more slip in the mid range with the engines in the 5th hole. (see the chart).
              2)
              Suggested maybe try Rev 4 XT 23p since these are the fatter gear cases.
              .
              You had mentioned Bravo1 FS slip near 15-20%. My slip numbers now- at WOT- are 5-6%. Is that the direction I want to go? Not sure I understand here.

              Your thoughts please.

              Do you have a set of Rev 4 XT 23's?

              Thanks,

              BIll

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              • #8
                He's talking about the Rev 4 XP
                Its just a modified Rev 4 They thin the blades a little with the (pro finish) and it likely has a little less cupping, but I've only ever compared them one time on the Rev 4's, and it wasn't a great comparison.
                Had a guy with triples that ran the Rev 4 XP's 22's on the outside and 23 XP in the center.
                He compared them to 21 stock Q4's (same prop as the Revolution 4) and it was 4 MPH slower. but, it was a different pitch.
                Put 23's all the way across. (again, Q4's) and the motors couldn't turn them, it was slow and low on RPM.

                Would have liked a cleaner apples to apples pitch to pitch comparison, but maybe one day I will.

                I don't stock either (Bravo FS or Rev 4 XP) for testing unfortunately.
                I only have the stock Rev 4's and Bravo's

                I mentioned the Bravo FS slip numbers so you know what to expect. They have less cup then a stock bravo, the slip numbers are normally higher, and you have to run a higher pitch because of that.

                Ken Reeves
                [email protected]
                941-735-5808

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                • #9
                  Ken.

                  Lots of information to consider. I know - more of an art than science. Nothings really points me towards any one prop, ....hey this is the prop for you!-------over the Bravo1 22p's I already have, and the numbers I'm running now. I'll keep researching.

                  Thanks,
                  Bill

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                  • #10
                    There is no "correct" answer.
                    Your numbers are great.
                    If you want top end, 24 FS props "might" gain a little top end. if I had to bet, I'd say 1 or 2 MPH.
                    Rev 4 XP's, I'd expecte about the same.
                    Economy, I'd expect the ECO's to get a tenth or so better in midrange, but likely give up 1 or 2 MPH on top end.

                    Ken Reeves
                    [email protected]
                    941-735-5808

                    Comment

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