Bad transducer location?

[Tiller The Hun]

I have installed a Eagle Fishmark 480 on my aluminum boat. It works perfect at low speeds but at any speed over 25 mph it loses bottom and the depth will start flashing on the screen. I installed the transducer according to recommendations. I even had a friend lean over the transom at high speeds and it seemed to be located in an area of little interference. There is a very slight rooster tail coming from the transducer though. Is it possible that it is not low enough? It is flush with the bottom of the boat right now.
I did install it on a transom plate so I could move it if I had to but it seems to be in the best location.
Any ideas? I am stumped!

[REW]

With many aluminum rivited boats, you need to have the transdcer at depths that may be as much as 1/2 inch lower than the bottom edge of the transom.

An easy way to check this out, is to temporarily remove the transducer from your mounting board.

Then take a 2X4 and attach the transom to the 2X4.
Have the 2X4 long enough so that you can reach to the top of the transom, plus a bit more.

Then, using a heavy c-clamp, clamp the transducer in the location, that you think that might work. Test it. If it works - great - mark the spot and mount it in place.

If not, move the transom up/down/ back/ or forth - until you find a place where you get a clean reading.

Take care
REW

[alanexpup]

Its not in the water far enough