Re: depth finders and in-hull transducers
Yup - some do have that problem. However a lot has to be attributed to their placement and how good a job was done in putting it down.
Too far forward or to either side and you'll have those issues.
Then there's the situation with the design of the bottom as well. Some step hulls are notorious for screwing up transducer readings due to their ability to produce a lot of unwanted turbulence - or bubbles.
Then, let's get right to the unit itself. The higher end stuff will give you a lot better read out on plane than the less expensive ones will. All is due to power output. I would definitely speak with a customer service rep for each unit you may have in mind. Forget the local salesperson. Tell em' what boat you've got and what you expect. A few phone calls now will certainly save you a lot of aggravation down the road.
My $.02
