The reason for the water is simple: transducers do not work shooting through air. A transducer spots fish in part by bouncing the acoustic signal off their air-filled swim bladders. The bigger the bladder, the bigger the fish, the bigger the blip. Even air bubbles in fiberglass or in a boat's wake can throw off readings. By submerging the unit in water, or light oil in some cases, it provides a contiguous signal path, interrupted only by the fiberglass in the hull. Check the transducer instructions for the right liquid.
PAUL ESTERLE
It sounds like a lot of work but once you've done it, you know the location is correct. Remove the tubing or pool of water and dry out the mounting area. You can epoxy the tube in place, cap it and run the transdiucer cable through the cap, if you choose. Either way, the transducer must be placed in the location and permanently mounted. Here is where practical experience differs from the manufacturers instructions. Most manufacturers suggest using a thick, slow setting epoxy to mount the transducer in place. Coat both the hull and the transducer and push the transducer in place twisting the transducer to ensure that there are no air bubbles underneath.
A more common mounting method is to place a large blob of sealant in the mounting area and push the transducer into the sealant, making sure there are no bubbles. This makes for a much quicker installation. Just be sure to have the boat in the water so you can test the accuracy of the unit before the sealant cures. Also, make sure you use the appropriate sealant suggested by the manufacturer, as some can attack the plastics used in the transducer. Avoid 3M's 5200 because it will be difficult to remove the unit later if you want to replace it.
There are some special considerations in mounting transducers in metal or wood hulls, which should be covered very well in the manufacturer's installation directions (another good reason to preview the manuals online before you buy).
Like most of the projects aboard our boats, it isn't rocket science. But it does require that you pay attention to the details and follow the instructions. Do that and you will be tracking down those big fish pretty quickly.
Paul Esterle is Technical Editor for Small Craft Advisor Magazine, and his freelance work has appeared in Sail, BoatWorks, Voyaging and Good Old Boat magazines. He has produced a series of boating videos and lectures widely. He also works at West Marine and has written product reviews for the company.
