23 Seacraft Suzuki 300AP prop help

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  • 23 Seacraft Suzuki 300AP prop help

    I have a 1976 Seacraft Sceptre with a 2017 Suzuki 300 transom mounted that has not been getting the efficiency I'd like to see. It came with a 3 blade 15x21.5 Suzuki prop and after looking at the slip numbers (4000 rpm, 25 mph - 36% slip) I figured changing to a 4 blade or a 16" diameter should fix this issue. I picked up a Bravo 1 LT 20p and tested it out a few days back:

    3500 rpm, 19 mph, 40% slip
    4000 rpm, 26 mph, 29% slip
    6125 rpm, 45.5 mph, 18% slip WOT @65% trim

    Overall, the Bravo feels a bit better and MPG is slightly better (3.0 mpg vs 2.8 mpg at best cruise around 22 mph). It seems to hold a plane a little better and seems to give the boat a better ride by slowing down pitching perhaps? (not sure about this as I've only had it out once so far)

    Both props have reasonable holeshot and the boat feels nicely balanced, I don't use any tab unless in a strong crosswind or running under 20 mph.

    The slip does seem excessive though and I am hoping to get over 3.0 mpg if possible. Not worried about top speed as I am in the ocean 100% of the time.

    There is an abandoned thru-hull transducer fairing mounted to the keel directly ahead of the motor (it used to have twins), could turbulence from the transducer be causing the prop to slip?
    The motor is mounted a bit deep with the cav plate even with the keel at normal trim.

    Also, the boat has a large hardtop/tower, so I do expect to be a bit slower than others with the same setup.

    I'm thinking about trying an LFS4 18p or maybe a Solas L3 plus 19p for even more grip, but if the transducer is the issue maybe I just need to bite the bullet and dig that thing out of there....

    Thanks, Jonah



  • #2
    The LFS4 would be my choice as well, but I would absolutely get that transducer out of there first. It could be causing the problem for sure.
    When you remove that, you may end up just fine with your current props.

    Ken Reeves
    [email protected]
    941-735-5808

    Comment


    • #3
      Okay, thanks for that.. I'll see if I can get that thing out of there first and go from there

      Comment


      • #4
        Hi Ken,

        So finally got back out on the water after removing the old transducer and the numbers are pretty much identical; 19 mph @ 3500 & 26 @ 4000 so 30-40% slip at cruising speeds.

        Do you think the next step is a 16 diameter 3 blade or all the way to the LFS4? The other knob I can turn at this point is to raise the motor up a couple of holes, but I don't see that making that much difference with the slip numbers.

        Thanks, Jonah

        Comment


        • #5
          I'd go LFS4, 18 pitch and we'll see what happens.
          cost $499 from me, 35 if we need to swap out or return it.

          Ken Reeves
          [email protected]
          941-735-5808

          Comment

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