Soundings

The Chartplotter depth display reading the depth beneath the boat in the marina at low tide.

The instrumentation on my boat is as old as I am and half of it does not work. My depth sounder was one of the remaining function instruments. It was a older signet "digital" model. It was never entirely effective and half the time it read the keel. Finally one of the digits on the display burned out meaning that it was accurate to within 9 feet.

With the demise of my old depth sounder I had to move over to my "analog" back up, the keel. I did have a back up plan however. When I purchased my Lowrance Chartplotter off of craigslist the guy had mentioned that it had a depth sounder transducer. It was one of those transom mount ones and when I bought the device the transducer was still attached to his boat. He said next year I could pick it up. A year later I emailed him and got the transducer and kept it in a box. Now I had to figure out if it worked.

I spliced in some new coaxial cable and hooked it up to the Chartplotter, no sparks. I then through the transducer over the side of the boat and immediately began getting readings. I hauled it aboard. These transom mounted transducers are designed to be mounted to the stern of a power boat but that is impossible on a sailboat. Sailboats usually have thru-hull transducers. There is a way to mount a transom transducer inside a sailboat. It sometime doesn't work. Basically you have to have a non-cored hull and have no air between the transducer and the hull. You can make a wet box or use a silicone/epoxy to mount it to the hull.

Under one of the settees I found a puddle of water and I put the transducer in it and began getting readings. I now knew that my hull could conduct the soundings and that I needed to find away to mount it. I opted for the silicone solution. I used 3M's 5200 marine adhesive. I globed on a 3" square blob of the stuff where I had tested the transducer and simply mashed it into it. It is important that there are no air bubbles so I immediately tested it and found that it worked.

The Transducer in its bed of 5200 sealant.

I spent some time tidying up the wires. A few days later Curtis and I took the boat out for a sail and we fired up the depth sounder and it worked like a charm. I offset the soundings to account for the WEASEL's 5'2" keel. The next step is to calibrate it by taking a weighted line and measuring it. I may then have to tweak the settings to make sure that it is operating correctly.

While I will purchase a new depth instrument when I replace all of the others I am covered until then.