If you are not getting a good reading at speed, it's due to turbulence creating air bubbles below the beam. You will have to move it to get it in clean water....up, down, left, right, tilt in or out. Could be a small movement, could be a large movement....might even have to relocate it.

Worst case, you could "glass it" inside the hull and you should get a good reading.

That will be one boofey please.

Wannabe...