I've always said that depth finders are good for idle speed exploring and reconciling your position on a chart (depth trend) at those speeds only.

Fever Mike,
You're correct that a person should know where he is and the depths. I've talked with Airmar and there transducers are capable of reading bottom to some pretty high speeds. I'm done.
ed

Yes mounted off the transom (deep mounting) on a traditonal V with no aeration to the water you can read the bottom at really high speeds. When I had my 36 Concept which is a traditional deep V I reset the transom mounted trasducer (Airmar) deeper in the water. On smooth water I could read the depthfinder/sonar on my Garmin 2006C all the way up to 55-60mph. However I lost some spped due to the extra drag. There are also front and side shoot sonars too but they are very expensive.

My non stepped 27 had the transduced mounted in a PVC tube that was set into the floor of the bilge. It worked flawless as fast as my boat would go, 83mph.

My stepped 32's quits reading as soon as the boat is put in gear. Even at idle it wouldn't register. Craziest thing I ever seen. Removed the depth gauge and installed my stereo remote in that location on the dash.
To bad Merc couldn't incorporate a sender into the lower drive unit.