Robalo R190 and Yamaha F115 prop question.

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  • Robalo R190 and Yamaha F115 prop question.

    I have a new to me 1973 R190 with a 02 Yamaha F115 on a stainless marine bracket. I was able to put about 10 hrs on it before I found out the previous owner had used JB weld to fix some missing metal on the cyl head. Anyway should be getting it back very soon. It currently has the black Yamaha 17K three blade on it that has some dings on it. I’m getting around 31MPH gps speed at 5700-5800 rpms with a medium load. I have a suspicion that the motor is mounted a little high since I can’t trim up much before you can hear it ventilate. Also ventilates quite a bit in turns. Also as I raise the tabs up it wants to start porpoising. So those numbers are with the tabs pretty low in the water. The motor is currently mounted as low it will go so I’m pretty much stuck with the height issue. I’m wondering if a 4 blade could help with the ventilation issue and the pretty high slip numbers. I believe the calculator said it was 25% slip or so. The 4 blade power tech semi-cleaver seems like it might be the way to go? Curious what pitch to get though. Any advice would be greatly appreciated

    Thanks

    Josh

  • #2
    I agree on the SCD4.
    If it hooks up well, like we hope it will, I'd expect around 10% slip.
    I'd probably try a 16 pitch.

    If the SCD4 still doesn't hook up enough, the next option would be the RXB4. which has much better traction.

    Both cost the same 375. you could just go straight to the RXB4 and see what happens.
    I'd probably go 15 pitch with the RXB4. it normally hooks up strong.

    Ken Reeves
    KR@Propgods.com
    941-735-5808

    Comment


    • #3
      Ken,

      Thanks for the quick response. Ok between those two would would one have more potential to help with porpoising or are they equal in that regard? Also, once I have more than 4 people, 45 gals fuel etc. it noticeably increase time to plane(Which is to be expected I guess). Would one or the other help with the hole shot? The boat is probably underpowered but hopefully we can find a happy medium.

      Also I’m South Pinellas not far from the skyway. Would it be easier to meet you in Sarasota then shipping?

      Thanks,

      Josh

      Comment


      • #4
        The Powertech props drop ship from Powertech which is in Louisiana. so gotta ship it either way.

        Both give decent sternlift.
        The RXB just has more bite/grip.

        Lots of unknows.

        It does look fairly high in the water flow on that picture, which makes me lean toward that RXB4 first.
        But if you load with 4 guys, 45 Gal of fuel ect a lot of the time, I'd go 14 pitch.
        however, you might be able to turn a 15 pitch, if you don't have to run with your tabs dragging all the time.

        Either would be a better option then the current prop.
        The SCD4 is a great sternlifter, and gives good holeshot, just want to make sure it has enough bite.

        I think a 15 RXB4 would be the safest bet.

        Ken Reeves
        KR@Propgods.com
        941-735-5808

        Comment


        • #5
          Ken,

          Alright that sounds like a winner. Yeah id prefer to try the 15 pitch if it will spin it. Thanks again for all the info. I’ll be giving you a call sometime this week.

          Thanks

          Josh

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