toying with idea of a fish finder

I have read instructions about mounting with goop so that transducer shoots through the hull, but the instructions I have read refer to plastic boats. Will this technique work on a fiberglass boat? And does mounting inside vs outside affect the range or resolution?

Are most or any units sold independently of the transducer? If I wanted a suction cup mount, would I need to look at specific models that are made for that application, or can the transducer for most any model be mounted any way you want?

Also, are any models favored for kayak use? Are there 50 or 2 or 3 to choose from. FWIW, I would prefer one with an internal battery.

Finally, was just at Humminbird site and was asked if I wanted to see fresh or saltwater models. Does this make a difference? I would like to use it in both environments.


Most transducers work through
fiberglass as well. I’ve also had several on powerboats in the past and even a fairly thick hull won’t alter their effectiveness. It does, however, need to be epoxy’d to the inside of the hull.

An alternative to gluing, other stuff

– Last Updated: Dec-03-14 8:04 PM EST –

You don't have to glue the transducer to the inside of your hull to shoot a signal through the hull. Instead, you can glue a short piece of PVC pipe (about two inches long) to the bottom of the hull, pour some water into it, and set your transducer in that water. I've used that method on my chopper-gun fiberglass motorboat, and on fiberblass/kevlar boats. I can't say for sure that it's as good a method as gluing the transducer to the hull, but it works pretty well, and you are free to use whatever boat you want, not just the one with the transducer glued inside. Do you want the transducer and (most likely) 15 feet of coaxial cable in your boat even when you aren't fishing? What if you get a different boat and want to use THAT one for fishing?

One thing with the above-described method, is that the inside surface of the hull must be clean. A thin layer of algae at the bottom of that little container of water will really block the signal. I can't figure out why it should (after all, the material is water-soaked), but it does.

By the way, when I glue a piece of PVC pipe to the bottom of the hull, I use silicon sealant. That's a non-permanent attachment method. I can remove the piece of pipe in an instant if I won't be using the boat for fishing for a while.

As far as suction-cup mounts, all transducers I've seen have a provision for being bolted to something. If you are inventive, you could make an external mount that attaches to the boat by some method other than a suction cup.

On the subject of true portability (and that means internal batteries), this type is getting scarce. It makes no sense to me, but they seem to be being displaced by depth sounder functions that can be displayed on your cell phone (who'd rather look at their cell phone than a purpose built screen that can be aimed where you want it, especially when depth sounders can be rained on and splashed, but cell phones can't). I haven't done any serious shopping for a depth sounder in ages so I can't list any current models for you. Also, in the realm of portable units, you may not be able to find one that displays actual graphing of the echoes that it "sees". Instead, you'll probably be stuck with one that displays an enormous 'cartoon fish' on the screen every time there's an echo that's not on the bottom. Ninety percent of all mid-water echoes are NOT fish, but even if they were, I'd rather see them graphed on the screen as a true interpretation of the echo and make my own decision about what it is (you won't see cartoon fish on any of the non-portable depth sounders in the motorboats of good fishermen - all you will see is straight graphing). Okay, you can see that I really dislike cartoon fish on the screen. One portable model that shows a true graph instead of cartoon fish that USED to be available is the Vexilar "Boundary Waters." I have one, and the graphing quality is excellent for such a tiny unit (and did I mention NO cartoon fish?). If you can find a used one for sale somewhere, I'd recommend it.

very interesting
I’m trying to visualize this. Is the short piece of PVC mounted vertically (so that you fill it from the top and just stick the transducer in the water? And what approximate diameter of pipe do you use? As for icons……not a problem that fish icons are not necessarily fish as I’m actually much more interested in detecting mermaids. Do any models have mermaid icons and, if so, do you know anything about the false positive rate?

You’ll have to keep me posted on what you find out about detecting mermaids. I’ve never been that lucky.

For the PVC pipe I was talking about, in actuality, it’s a coupling for PVC pipe (getting a coupling is the easiest way to get a short piece if you don’t have pipe on hand), and yes, it is glued to the floor “end-wise” so the top is open and it can be filled with water. I think the size I use is about three inches in diameter and about 1.5 inches high (long), so I believe I probably cut the coupling in half to make it shorter. I think as long as the transducer fits inside the pipe/coupling, it will do the job.

You may want to make a way to stabilize the transducer when it’s in that container of water. It may tend to get tilted to the side on account of the heavy cable that attaches to it.