Duck-- Here's what I would do: first call 800-633-1468. That's the Humminbird customer service line. Do this when you've got time because they can be busy. Humminbird bought Bottomline two-plus years ago, so they are the folks you want to talk to. Also realize that this brand is an orphan; only the Fishin' Buddy depthfinders still exist, and I think those are now Humminbirds.

You still should be able to get service from the company, but...parts may be a different story.

I know very little about depthfinders as far as making them sit up and do tricks. If you've done the re-set of defaults and played through the manual, then you've done what I would suggest from the software side.

What I would check from the hardware side is interference (as suggested earlier) from trolling motor wiring, transducer location, the battery and connections and the transducer itself.

Since you're running this off a 'toon, you probably aren't using a trolling motor, so interference isn't an issue. I would re-check the battery and connections to make sure the power supply is what is needed and that you have a good flow of juice with no corrosion or anything that might limit the flow of electricity.

As for the transducer...if it is fully in the water and not mounted above it (gotta point that out) on the curve of the pontoon, then location is probably fine as long as there isn't anything that might float under the transducer like a strap or flap or whatever (going from my own experience here). As you're probably aware, transducers don't shoot through air very well, and they don't shoot through things containing air (such as wood or foam).

The last thing I would check is the transducer itself. Sometimes there is a buildup of crud on a transducer and a light sanding of the face will get rid of the problem. It could be that your transducer has a build-up of finish or coating or crud of some kind. I would first check with the above folks at Humminbird to make sure that doesn't invalidate your warranty.

If you're given the option, I'd trade for a Humminbird unit in a minute. Bottomline had a lot of problems in the later years of production, and the new 'birds don't. I've got two on my boats and like them. Even the low-end Humminbirds are good units.

Hope this helps.

Keith