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  1. #1
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    Let's Set This Thing Up?

    I have begun an adventure in a new realm...mini tunnel hull! I have a 4060 Regal Express Yacht, and wanted a more interesting "dinghy", so I came across an opportunity to acquire a 1986 Baja Scat Cat, and I got it. Of course now the true challenge begins...how to get this thing properly set up? If you are familiar with these, they are a 12' tunnel hull, that was originally fitted with a 25hp outboard...mine however has been equipped with a 1976 Mercury 500 2-stroke (50hp) tilt/trim, with small whale tail and the A/V plate about 1" below the primary tunnel/transom (jackplate), motor is fitted with a 3-blade aluminum prop (11x12p, cupped to 14p), and fuel tank is in the bow. So here is what I experience...planes relatively quickly, although tends to ventilate the entire time...on plane the A/V plate is just at/below the water surface with frequent ventilation and what seems to be a plowing bow (water breaking ahead of my seated position). Trimming up does not raise the bow, and will only continue to cause ventilation. No chine walking, and seems to steer/handle well on plane. WOT is 5,000 rpm, which is on the low range for the 500 Mercury.

    I have only tested one alteration so far, and don't really want to make many adjustments until I can get some input from "those in the know" on this forum. I took the whale tail off and ran it, but the boat would not plane under about 90% load (my wife was with me), until she sat on the bow. Once on plane, it would hold with her back in the normal seat position, but all other issues/experiences remained the same as with the wing once on plane. First I want to make sure that the engine is mounted at the right height, as I believe it may be low based on the A/V plate position at plane, but I thought raising may increase my bow plow and ventilation issues. Second, once the engine is properly positioned I want to equip it with the "right" prop...type and size? I am considering an 11.25 x 14 s.s. semi-cleaver, but I don't want to get ahead of myself.

    Please share the wisdom that I know exist on this site! Thanks.

  2. #2
    Join Date
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    I see a lot of threads about these small cats but usually not a lot of good feedback on how to get them to run well. Best of luck getting your to run well.
    I dont think a cleaver style prop is the answer. Cleavers typically only run well when gong very fast. Holeshot and midrange usually suffer. Your little cat need a prop with a lot of blade to get t up on plane and stay hooked up. You might try something like a Mercury Laser in an even pitch which as the small tube or a Trophy Sport if they can be mounted to your motor.
    13' Biel tunnel AKA "Flight Risk"
    13" Modified Yamaha V4 - 101 mph

    21' Paramount
    Mercury 300 Promax

  3. #3
    Join Date
    Jun 2004
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    Boynton Florida
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    @CTMalone did you ever figure out your setup for top speed. I have one myself and im trying to figure it all out. Thanks

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