If the 549' depth reading happening when you are under way, say, anything
about an idle. Then you need to adjust your transducer's alignment with the
hull. Generally, the front of the transducer should the slightly higher than
the rear. The bottom of the transducer should be just a little below the
transom, about 1/8"-1/4". What the adjustments are trying to do is get a
clean water flow around it (no bubbles and minimum turbulence ) .
For the speed, maybe your transducer is missing the optional paddle
wheel/temperature sender? Temp and speed are optional on some of the
Hummingbirds.
Most units like Hummingbirds may never read properly while planing. If you
are getting a useable graph then things aren't so bad.

--
Ron White
Boat building web address is
www.concentric.net/~knotreel