I replaced my depth meter today after a week of chasing after a suitable replacement. The old unit was a Uniden model which had got sunburned (no UV protective cover) and eventually the plastic lens cracked, allowing water to ruin it. I paid around $100 for it about 5 years ago.
I planted the old transducer inside the hull just in front of the keel in a bed of silcone sealant (one of the few legit uses of silicone on a boat), and it has worked okay. It never recorded depths lower than 35 feet consistently – it would blink an error response after a while – but would always come back on line when the water began to shoal. Around 25 feet it would begin to report depths consistently again. And this seemed fine to me, as my biggest concern was knowing depths as the water got shallow.
I had hoped that I could use the old transducer with the new unit, and as I did some research I discovered that the transducers both operated at the same frequency and power output (200 kHz; 250 watts). The connections were different at the display head, but a bit of work with nippers and crimpers took care of that: I cut off the plug from the new transducer and spliced on to the coax of the old. Upon power-up, it began reporting depth at the slip with no error messages. Success! That saved me an hour or more of crawling around on hands and knees in tight spaces to install the new transducer, and another hour of routing new coax to the gauge.
The new unit made by HawkEye ($105) seems to be more robust. Whereas the Uniden had a plastic lens, the Hawkeye lens is glass, and includes a UV cover for the unit. The Hawkeye also omits the gain control in back, claiming that the algorithms programmed into the unit make it unnecessary, so I’m hoping for better performance overall compared to the old unit.
I bedded the new unit in butyl putty/tape, rolling a small amount in my hands until it became a thin worm about 6 inches long. I tucked this around the gauge’s flange and pushed the unit against the bulkhead, tightening it with the little bracket and knurled wheel they supply for installation. This is so much better than using goopy, messy caulk.
Finally, we’re in the summer weather pattern here in Maryland, with frequent afternoon rain storms – I was happy to finish the installation just in time to clean up and close up against the rain, which began 10 minutes later.