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Thread: Trim Tabs???

  1. #1
    sk1981
    Have a 1997 SR 21 foot Advantage Step hull with a 454 @ 425hp. At 70 mph get a really bad prop walk. (really squirlly) Connecting rod went through the block and will be putting a 540ci dart 600hp motor. My question is for trim tabs to stop the prop walk with added hp. Can i go to big? ie. 30" or will some other combo be better. Options are 30" 24" and 17". By adding to big of a trim tab will I hurt the MPH. I am not worried about over kill becuase the is no price difference, just dont want to hurt the speed or performance.

  2. #2
    ULTRA26 # 1
    Have a 1997 SR 21 foot Advantage Step hull with a 454 @ 425hp. At 70 mph get a really bad prop walk. (really squirlly) Connecting rod went through the block and will be putting a 540ci dart 600hp motor. My question is for trim tabs to stop the prop walk with added hp. Can i go to big? ie. 30" or will some other combo be better. Options are 30" 24" and 17". By adding to big of a trim tab will I hurt the MPH. I am not worried about over kill becuase the is no price difference, just dont want to hurt the speed or performance.
    24" tabs on a 21' boat should be more than enough. I wouldn't expect tabs to cure the walk problem, as walk is generally hull related. However, tabs will provide you some additional stability.
    Good luck with whatever you decide and be safe

  3. #3
    DMOORE
    17" tabs are more than enough for a 21ft boat. We only ran 24" tabs on 42FT Fountains. Remamber the more tab in the water the more drag also. As for the installation, if you mount them parallel with the water insteas of the hull, they have more of a progressive "engagement" if you will. Sometimes this will let you fine tune the ride easier and with less tab in the water.
    Darrell.

  4. #4
    ULTRA26 # 1
    17" tabs are more than enough for a 21ft boat. We only ran 24" tabs on 42FT Fountains. Remamber the more tab in the water the more drag also. As for the installation, if you mount them parallel with the water insteas of the hull, they have more of a progressive "engagement" if you will. Sometimes this will let you fine tune the ride easier and with less tab in the water.
    Darrell.
    I saw a Schiada with 24's on it last weekend. I thought they looked long. I spoke with the owner of the boat who stated the long tabs reallly helped. If it were me, I would be be adding 17's.

  5. #5
    sk1981
    if i were to place the tabs parallel to the water rather than in line with the boat how would i figure my my mounting location?

  6. #6
    DMOORE
    Basically, they would mount at the same location both ways. At the outside edge of the transom. The only difference is that instead of following the line of the bottom of the transom, you would raise the inside of the tabs so that they are parallel with the ground. Since the boat is 21ft long and lite, it will be more sensative of tab position than a big/heavy boat. Mounting them this way will give you a bit more control to get that perfect "set" when running. The trick with tabs , is use them just enough to settle the boat.
    Darrell.

  7. #7
    sk1981
    thank you for all the input

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