Here's what I found out. It looks like it is normal for this to happen. I've been on friends boats with either the same model or similar model and they all lose sensitivity (for lack of a better term) in their fishfinding capabilities at higher speeds. Now this is taking for granted that we are talking about the transom mounted transducer that comes with the unit.
Mine still reads the depth fine, I just lose the "marks" for fish. When you compare the transom transducer, to a thru hull transducer, that's when you see a huge difference. My friends with the thru hull see marks at high speeds.
If I see ANYTHING except the white screen while I'm running (like the precursser of marks) you might want to double back and check that spot out at lower speeds.
I'm getting more comfortable with the unit every time out. I believe we just have to live with the issue or buy a thru hull (putting large hole in the bottom), or shoot through hull (but you lose the water temp. reading with this).
If you keep the boat in the slip, keep your transducer clean. If fouled, it will even lose the depth reading until you clean it.
Best of luck with your new electronics!
5th (Marty)
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