Depth Sounder Installation
By Dale Mack
I've used Navionics navigation software on my phone for several years. Combine the latest electronic charts with an onboard depth sounder and I gain a lot of peace of mind when sailing unfamiliar waters.
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| Depth sounder swung into position in the companionway. |
I settled on a low-cost Garmin Echo 150 fishfinder for my depth sounder solution. My unit came with a transom mount transducer, the transducer sends and receives the sound pulses used to determine the depth of the water. Some depth sounders come with a thru-hull transducer instead of a transom-mounted one. Although each transducer's housing is designed for a particular application, both styles can be used for mounting inside the boat without drilling any holes through or into the hull.
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| The depth sounder's mount supports viewing from anywhere in the cockpit. |
Monochrome fishfinders (black & white) have all but disappeared as the cost of color displays have come down. My Garmin Echo 150 works great, has a very readable display and does it all for about 1 amp which is easily replaced by my solar panel when docked.
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| A rare monochrome fishfinder. |
Mounting the Transducer with Silicone
My goal was to avoid any new holes in the boat, so I borrowed the silicone installation method I used on my first Catalina Yacht, a C22, back in 1987. With this approach, the transducer is installed inside the boat against the hull using a blob of silicone. The transducer's sound waves penetrate the Catalina's solid fiberglass hull easily. I located the transducer in the forward storage compartment just forward of the porta-potti, in the bilge below the aft end of the v-berth.
Here how to install the transducer:
- Clean the hull where the transducer is to be mounted. Let it thoroughly dry.
- Use clear silicone so you can watch for air bubbles.
- Press the caulking gun tip against the bilge and pumped out a blob of silicone large enough to cover the bottom of the transducer.
- Spread a layer of silicone on the bottom of the transducer.
- Verify there is no air bubbles in the silicone.
- Press the transducer down into the silicone in the bilge and leave it to so the silicone can cure. I came in at an angle so the air could escape and then I went level for the final positioning.
- DO NOT move the transducer up and down during the installation process or you may get air bubbles in the silicone. Many failed silicone installations are the result of air trapped in the silicone.
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| The transducer in place. |
With the transducer in place and its cable attached to the depth sounder, I was able to test out the installation even before the silicone was cured. The beauty with a silicone installation versus something like epoxy is, that it can easily be re-installed if the first attempt fails. I used a weight tape measure to verify the accuracy of the depth sounder readings while being mindful that the tape would read slightly different than the depth sounder because the transducer would be mounted a few inches below the waterline.
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| An air-free transducer installation. |
Swing Arm
I had seen a Catalina 22 with a VHF radio and a depth sounder mounted to a homemade swing arm, so I had already decided to replicate a version in teak for my boat.
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| DIY swing arm on a Catalina 22. |
While cruising the aisles of a second-hand marine consignment store, I ran across a beautiful instrument mount swing arm executed in aluminum. I choose the port side of the cabin to lessen the cables runs from the transducer in the bow, and from the switch panel for power. Celtic Myst, #239, is a 1987 model. All cables run below the molded-in V-berth and the port side seats.
The depth sounder has been a great addition to the boat. Bonus feature, the display is readable when in the storage position.
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