Electronics, GPS and VHF, Part 6: Transducer Installation

The Airmar B60-12 transducer, fully installed
A transducer is a useful electronic device on any sailboat. Without a transducer, the mariner is left wondering what the depth of the water might be. Of course he could use a lead line to determine this depth, as mariners before him did for centuries (and as some mariners still do), but the transducer has the benefit of providing an instant indication of depth - information that could help him quickly steer clear of water too shallow for his keel or centerboard. Some transducers bring with them additional benefits, such as temperature readings. Such is the case with the Airmar B60-12 transducer, the type of transducer that I installed in Oystercatcher, my Ericson 25. In this posting, I describe my rationale for selecting this particular transducer, and I describe the various steps that I took to secure it to the hull.
The location that I selected for the installation of the transducer was within the largest of the three lockers in the V-berth area of the boat.
This through-hull transducer in the V-berth would relay its information to a Garmin brand GPS (GPSmap541s) in the cockpit. Garmin does not manufacture its own through-hull transducer for this GPS. Rather, it tools its GPS for the Airmar brand transducer.
As I said in earlier postings in this article, I opted to use a flush-mount kit for the installation of this GPS. This meant that the face of the GPS would be oriented toward the cockpit and the back of the GPS would be exposed to the galley. In the picture below, I am making sure that the transducer cable fits the appropriate connector in the wiring harness.
This transducer was of heavy-duty, bronze construction and contained a lengthy cable. I opted for bronze instead of plastic because of its durability. I opted for a through-hull style transducer because this style are more accurate than other styles. Was this transducer expensive? Yes, but I got for about half the suggested retail price through price-matching at West Marine (back when West Marine still did this sort of thing).
Also in the box with this transducer was a rubber gasket. This gasket would of course sit between the nut and the hull on the interior of the boat.
The Airmar B60-12 carries the number 12 designation to indicate that it can accommodate a hull with a deadrise up to 12 degrees. I liked this "tilted element" feature of this transducer. It meant that I did not have to install a wedge-shaped block of teak on the hull to level out the instrument.
Before I ever purchased this transducer, I had determined that the deadrise of the Ericson 25 is 12 degrees.
At the time of purchase in the fall of 2009, this boat had two different instruments in the aft locker of the V-berth: a defunct transducer (pictured left) and a defunct paddle-wheel knotmeter (pictured right). As I described in my four-part article "V Berth, Aft Locker, Holding Tank Shelf," I removed the knotmeter and filled the hole with fiberglass. This was where I would install the holding tank shelf.
Also, as I described in that article, I removed the old transducer for the purpose of replacing it with this new one, i.e., the Airmar B60-12.

Likewise, I described in that article how I enlarged the old transducer hole to make room for the new instrument.

After I had installed the infrastructure to support the holding tank and a large storage shelf in this space, I applied two coats of two-part paint. All of this I documented in the above-mentioned article.
In the midst of my work on the holding tank in the aft locker of the V-berth I had sanded the hull and applied two new coats of bottom paint. For more on this, see "Hull, Bottom Painting." Now it was time for me to rough-up the area around the exterior of the hole in preparation for the installation of the transducer.
With that quick and easy job out of the way, I proceeded with a dry-fit of the transducer.
It's important to orient the transducer correctly. Otherwise the tilted element within the instrument will not tilt in the manner that it should.

Before I inserted the transducer into the hole I wiped the bronze with acetone to remove any oil that might have been on the surface from the manufacturing process. Did I pick up some residue on my cloth? Yes.
The transducer fit just right. Note that the plastic cap on the top of the transducer makes the orientation of the instrument idiot-proof.
Not only has Airmar placed an arrow that points toward the keel, but also it has constructed the cap in such a way that the cable must point toward the keel.
Satisfied with the dry-fit, I moved forward with the installation. For this, I enlisted the help of a buddy. One of us held the transducer, the other applied Sikaflex 291 LOT (Long Open Time) polyurethane adhesive/sealant.
Then, one of us inserted the transducer, while the other went inside the boat to secure it with the nut.
Very little of the Sikaflex from the exterior made it to the interior. Therefore, it was necessary to apply some of this adhesive/sealer in the area where the nut would sit against the hull.
Tightening the nut was a one-man job, but it was a job that required a set of Channel-Lock pliers in each hand. The small set was for holding the transducer still. The large set was for screwing the nut down tight. For those who might wonder how the small set did not damage the threads on the transducer, I should note that there are two flat spots within the threads that are designed to accommodate a set of pliers. In terms of the tightening of the nut itself, I should mention that it's important not to screw it down too far. Otherwise, the nut will distort the rubber gasket. I myself went a little too far, and as a result, had to back it off a little bit.
Outside the boat, I cleaned up the excess Sikaflex with a plastic epoxy stir-stick and a rag moistened with mineral spirits.
I did the same thing inside the boat, shortly after I snapped the picture you see below.
All in all, after I had completed all of the prep work, the installation of the Airmar B60-12 transducer in Oystercatcher, my Ericson 25, was pretty simple.

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