23 Seacraft Merc V8 250

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  • 23 Seacraft Merc V8 250

    Hey there,
    about to repower our 1987 23 Seacraft center console with a new Mercury V8 250 and was wondering what prop you recommend we start off with?

    It’s a notched transom, 30” leg. Boat has a small pilot house, but probably similar wind resistance as a regular CC. We’ll run it average load. Holds 110 gallons of fuel, and we usually try to keep the boat light. Just 2-3 people and gear.

    Thanks!


  • #2
    Do you have the 1.75 or 1.85 gearcase. should be on a sticker on the antiventilation plate.

    what was your old motor? what GPS speed did you get at wide open with your old motor, with the boat loaded up like you actually use it most of the time?

    Ken Reeves
    [email protected]
    941-735-5808

    Comment


    • #3
      haven't received the new motor yet, but it's a 1.75 gear ratio gearcase.

      the old motor is a 250 OX66. it has a Q4 4 blade prop 14.6 x 17P. it normally topped out at 43 mph with a regular load. it ran good with the 4 blade, but I wouldn't mind a little more speed. normally cruised it at 30-33 mph.

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      • #4
        Well, might as well try that prop on the new motor.
        What RPM were you turning at 43 MPH?

        You'll need a racing hub, I have them for 150 bucks, but your local dealer probably has them for the same.

        Your old motor has a 1.81 gear ratio, the new one has a 1.75, so at any given RPM, you'd expect slightly more speed.
        If we know your RPM at 43 MPH, we can figure out the slip ratio and see what to expect with the new motor.


        Ken Reeves
        [email protected]
        941-735-5808

        Comment


        • #5
          it was right around 5200-5300.

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          • #6
            what would be a comparable 3 blade to try? what about those Eco-Inertia's? have heard a lot of people running those.

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            • #7
              ECO is nice, but 17 is the lowest pitch they make, and I don't think you'll be able to turn it.

              at 43 MPH with your 17 Rev 4 getting the same slip ratio you were getting before, (9%) you'd only be turning 5150 at 43 MPH with your new motor.
              But if the old motor was a little weak, and you gain some speed, then maybe you can turn the 17 Q4.
              if you manage to get 47-48 MPH out of the boat, you'll be turning 5600-5700

              If you were going to go 3 blade, I'd probably want to try a 16 pitch standard Enertia.

              but I'd definitely throw that Q4 on there.

              Ken Reeves
              [email protected]
              941-735-5808

              Comment


              • #8
                I played with prop selector on the Mercury website. They came up with the mirage plus 15” or rev 4 15”. But I’ll definitely try the 17” q4 as you suggested.

                Thanks so much for your help! Will report back what we find.
                Attached Files

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                • #9
                  Yeah, I'm not a fan of the 15 Revolution 4, every time I've personally tried it on a boat, it ventilated badly, but its been years since I did that, so maybe they fixed them by now.
                  and I agree, very good chance you can't turn the 17 Rev 4, the only way you will is if you gain some significant top end speed.
                  If not you'll need a 15 pitch.

                  The two 15's I like are the Quicksilver Q3 (same as the Enertia) or the Quicksilver Thunderbolt, (same as the Mirage Plus)
                  I think the Q3 would be a good fit for your boat, and its offered in 15 or 16.

                  Once you run your 17 Q4, we'll know if your going to gain any speed or not.
                  If your still stuck at 43 MPH, it will be between a 15 or 16 Q3

                  Ken Reeves
                  [email protected]
                  941-735-5808

                  Comment

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