fish finder noise

I have a echomap 73sv with a CV40 transducer. Everything works fine (besides down imaging not being as crisp as I'd like because of the CV40) except I get a lot of noise when traveling at speeds greater than 2-3 mph. I have a Lund so I have rivets on hull. I didn't pay attention to this much when mounting my transducer but I'm about 3in to the right of a rivet line. the bottom of my transducer is slightly below the bottom of the hull and level when out of water. I'm thinking I may need to tip my transducer tip down more but does anyone have any recommendations? Am I still to high? Do you think angling the tip down more will help with this problem?

Any thoughts?