Robalo Cayman 226

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  • Robalo Cayman 226

    Have a Robalo Cayman 226 with a SHO 250.
    Hardtop, 5 batteries, “two rear & 3 head”, two chargers, electronic package, power pole, trim tabs, Bobs 6” jack plate, 72” Minn Kota,

    these are are the numbers I am getting. On my third Propeller. Motor all the way down. 3/4 tank of fuel and two people, no gear.

    What im trying to accomplish. Get my WOT as high as possible to be able to drop down to a 40 mph cruise with the best mpg I can. For running offshore.

    “First prop tried”
    PowerTech 4 blade
    OFS4 15.25 x 19
    50 MPH WOT @ 5000 RPM
    2.1 MPG
    40 mph @ 4200 RPM
    3.0 mpg

    “Second prop lost top end and cruise mpg & gain 300 rpm on wot”
    PowerTech 4 blade
    OFS4 15.25 X 17
    46 MPH WOT at 5300 RPM
    2.0 MPG
    40 mph @ 4600 RPM
    2.3 mpg

    “Current prop”
    Yamaha Saltwater Series II 3 blade
    15.25 x 19 SDS
    WOT 48 MPH @ 5700 RPM
    2.0 mpg
    40 mph @ 4300 RPM
    2.7 mpg
    Thinking I should get more top in then 48 mph.
    48 mph When not trying to break loose and cavitate on lite chop in upper rpm.

    The PowerTech 4 blade 19 seemed to not cavitate, hold better any position on jackplate and have best mpg at 40 mph. But not getting my WOT RPMs.

    Only 8 hours on motor.
    Last edited by Shoalkat; 03-09-2019, 11:33 PM.

  • #2
    You said, "motor all the way down"
    I would trim and jack each prop to the height and trim level where you get your best speed.
    So at wide open, trim it up, jack it up, as long as the speed is improving, thats good.
    At some point, if you go to high, or trim out too far, it will gain RPM but the speed will drop off, we won't count that RPM.
    just get the RPM where you find your best speed.

    I would have expected much better numbers from that 17 OFS4. that is a huge drop in economy at 40

    Ken Reeves


    • #3
      Thank you Ken
      I will run back to the lake today. Only have this 3 blade 19 SDS right now. I found the last time I ran it with the 19 three blade, in a lite chop running 41 Mph, I would see at times the rpms increase to around 4800, like cavating, gaining rpms without speed. I did try running jack plate up and down.
      Actually saw no speed increase with little rpm increase on the PowerTech 19. I would say it felt good and held tight on the upper end. If it got the rpm up at wot. Would had been pleased. Cruise was great on mpg and 50 mph is fine with me. Looking at a bunch on prop test and size and motor. I would think I could get mid 50’s.
      My boat was purchased with no JP. I added a Bob’s 6”. Motor is on bottom hole and the cavitation plate sets 1 1/2” higher then where the motor was directly mounted to boat. It was mounted directly to boat in second hole.

      Right now with motor motor all the way down, I’m 1 1/4” from hull bottom.
      Question, does a Lowrance StructureScan 3D transducer in front of the motor affect the WOT speed? Really no where to put on stern of boat with the way key slot is and trim tabs.

      One pic has a F200 on boat. At 30 hours. I removed the F200 and added the sho. Pic to show trim tab via transducer location. The reason for upgrade. I like a boat the cruises 40-45 going offshore on calm days. I go out top, 40 miles with a little running here and there. My boat would top out at 41 mph. I would catch myself going from 28-30 mph cruise on up to 38-40. Getting 2 mpg. I have a 60 gallon tank, ideally I would be able to go about 120 miles on a tank running wide open at 40 mph. So I got a SHO thinking I could get a top speed around 55 and back it down to 40-45 and get better mileage. If I was cruising at 3.0 mpg. That’s 180 miles to a tank. Nothing else, a piece of mind. And I don’t have to hammer my motor cruising in and out going offshore.


      • #4
        PowerTech OFS4 19
        Top out at 50 mph and 5000 rpm
        40 mph and 3.0 gpm


        • #5
          PowerTech OFS4 17


          • #6
            Yamaha SW II 3RH 19

            Upgraded the radio, same boat.


            • #7
              Question Ken
              I see bulletins 14.5 x 21 3 blade props getting 55 mph and 6000 rpm. That prop is no longer available.
              Going 3 blade different prop then the SDS? Still have the non slip at high rpm.

              Thoughts on a
              14x21 Solas Titan HR 4 blade
              14.25 x 21 Powertech PTZ4, SFS4, PTC4
              ideal on a three blade?

              fixing to load up to head to lake.


              • #8
                If you want a bowlifting 3 blade similar to the Yamaha Pro Series, I'd try a Mercury Tempest Plus.
                I'd try a 19 pitch though.
                You would only get the RPM if you gain some top end speed.

                Cost $30 to try one.

                Ken Reeves