There is supposed to be some play in the transducer. This is to help keep the transducer from getting damaged if it hits a stump or log.
I would make sure you have the bolts tight on either side that lock the transducer to the bracket (they have the lock washers you put in). Don't over tighten them, just make sure the transdcuer does not slip when you put pressure on it.
What I have also found is that the metal mounting bracket is sometimes a little too wide and gives the transducer bracket too much play. I would squeeze this together just a little until the play is down to a 1/4 inch or so. You still want it to be able to kick up if it hits something, so don't make it snug where it doesn't move at all.
Try this and let us know if it helps.
Good Luck,
Robert