I have a Humminbird Model 565 mounted on my 20' aluminum hulled boat. At speed the transducer kicks off a five foot high rooster tail. Is this a factor of the transducer simply not being low enough in the water?
Could also be too low in the water. Does your transducer bracket have slots so you can adjust the height of the transducer in relation to the bottom of the boat? The ones I have mounted call for the transducer to be even or slightly (1/16-1/8") under the hull. There also should not be any rivets or reinforcing pieces in front of the transducer if possible.