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Thread: Raising the X

  1. #1
    CBR is offline Platinum Member CBR's Avatar
    My Boats:
    Sonic 30ss
    Join Date
    Oct 2000
    North and South

    Raising the X

    I'd like to know if anyone on OSO with a twin engine 30ish foot boat changed their X dimension, by how much, and what speed they gained.

    I have a Sonic 1988 30SS and am thinking about raising the X by one inch. The boat is also getting Bravo I 24 pitch four blades fitted to the new Bravos and Scorpion motors going into it. Any other prop suggestions?

    Thanks in advance.

  2. #2
    Registered tomcat's Avatar
    Join Date
    Feb 2001
    I raised propshafts 2", 30 Excaliburcat with TRS. This is what happened:

    Before, propshafts 6.5" below hull

    25 Mirage, 80 @ 5200
    27 Mirage plus, 80 @ 4800, 66 @ 4000
    29 Mirage plus, 78 @ 4300, 74 @ 4000
    26 Bravo one, 78 @ 5000

    After, propshafts 4.5" below hull

    25 Mirage, 83 @ 5500
    27 Hydro Q IV, 84 @ 5000
    28 Bravo one, 82 @ 4800, 68 @ 4000
    27 Bravo one, 82 @ 5000, 63 @ 4000

    I would say that raising the drives gained 3 mph, but Mirage props would blow out, hard to plane with a load. Four blades were needed, slower, but got the planing back, little blowout with Hydro, none with Bravo. You lose ability to trim the bow as you raise the drive, not a problem with a cat where bowlift is by air, but you may not like it. Hydro had the least bowlift/ most sternlift. Was the fastest but I didn't like the way it felt, especially in calm water. All tests with props turning inward at the top, supposedly gives the most bowlift, maybe a bit more speed.

    I would try a bigger diameter three blade at the raised position if I could find one. The 29 Mirage plus is 15" diameter instead of 14.5", but I don't have enough power to use it.

  3. #3
    CBR is offline Platinum Member CBR's Avatar
    My Boats:
    Sonic 30ss
    Join Date
    Oct 2000
    North and South
    Great information TOMCAT, thanks!

    Anyone else with a V hull raise the x in their boat?

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