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Vent Holes 250ss prop

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  • Vent Holes 250ss prop

    Brand new. Just re-powered bass boat with a 250ss. Came with a 14.5 x 29 four blade. Hole shot is great. At cruising (3000-3500 rpm) if I step down on it the motor revs up quickly and is not biting or gripping the water until I feather it back. The prop has vent holes. Could these be the issue causing motor to rev up and not stay hooked up? Where do I find plugs for the Suzuki propellers. Thanks.

  • #2
    At 3000-3500rpm, I doubt the Vent Holes are doing anything. Vent Holes are there for Low RPM acceleration, making it quickly get into the upper RPM Range by Ventilating the prop a little.

    29" Pitch, is meaning you are running fairly High MPH, Are you running a Jack Plate? My though is you are Ventilating from running to High, not the Holes.

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    • #3
      So I plugged all the vents and dropped it back in the water. Hole shot is still fine. However it looses grip past 3000 rpms when I start trimming up to get the nose up still and when it does you can see the boat literally move up and down. Motor will also move sideways when it hooks in and out. Getting 5700 rpms but only about 65-67 mph. I have hydraulic jack plate so I’m moving it around too. So now the question is do I try out a 30 or 31? The 250 VMAX I replaced had a three blade 15 1/4 x 27 and never did this.

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      • #4
        Suzuki's seem to like to run shallow, They also tend to like Suzuki Props. And also like 3-4"s more pitch than a Yamaha. Kind of a different animals.

        That being said, I would work on 1 thing at a time. Max RPM while hooked up correctly.

        Then try lifting the Jack Plate till just pre blow out for Max RPMs.

        Then Cupped Props from there.

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        • #5
          Whatever prop you go with, you want your RPM target to be at least 6000rpm lightly loaded.

          Here is a link to Suzuki’s 250SS boat test page where ypu can see what people running similar boats have achieved and with what props.


          http://www.suzukimarine.com/Product%...2/DF250SS.aspx

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          • #6
            As I said brand new install and just baffled, them it occurred to me I did not see trim tab under ventilation plate so I checked it. Sure enough not one there like there was on the VMAX 250 (see pic). Could this be the culprit? Does your 250ss have one?

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            • #7
              3DA23338-98A4-4EA1-8362-6142274782C7.jpeg

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              • #8
                Should have a trim tab. But I doubt that is your problem. In post #3, you mention that it starts to ventilate when you trim out "to get the nose up." Also telling is your mention that "you can see the boat literally move up and down." I have a DF150, and a hydraulic jack plate. I do not need to trim the motor out very much at all when the motor is at the correct height on plane. The motor stays trimmed down pretty far compared to what was once required before I installed the jack plate. Your comment sounds to me like you are trimming out too far, causing the boat to porpoise and causing the ventilation. Once on plane, try adjusting the height with the jack plate first. When you get it at the correct height, the exhaust sound will change somewhat, and you'll know if you've gone too high if the prop starts to ventilate while trimmed down. After getting the motor at the correct height, you will not likely need much in the way of trimming out. If you then trim out too far, you'll get into exactly what you describe, porpoising and ventilation. You shouldn't have to lift the bow for best performance. When you're on plane, the whole boat lifts, not just the bow. Your boat runs fairly level while on plane
                Last edited by Harper; 02-13-2020, 10:56 AM.
                Mike
                μολὼν λαβέ

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                • #9
                  Originally posted by Moonlighter View Post
                  Whatever prop you go with, you want your RPM target to be at least 6000rpm lightly loaded.

                  Here is a link to Suzuki’s 250SS boat test page where ypu can see what people running similar boats have achieved and with what props.


                  http://www.suzukimarine.com/Product%...2/DF250SS.aspx
                  All of the Bass Boats on there are running 4 Blade 14.5x30" pitch, and 6250RPM. except the Blazer which is running a 31" @ 80MPH again 6250rpm.

                  Point being, 4 blades will grip better. and at 30"s I doubt the Trim Tab will fit anyways, which only helps with steering pull.

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