Depth Sounder
The old depth sounder had problems. First it was mounted in what I found to be an inconvenient location. I have seen other boats with the depth sounder mounted here but I don't understand why. Also the unit tended to flash "E 19" instead of displaying the depth after a while. I could not figure out why. Also I wanted a unit that was easy to read.
I had to install a new Raymarine ST 40 Bidata depth and speed instrument. I also had to put new antifouling on the bottom.
The original impeller
The zinc plates
The original impeller removed
The depth transducer removed. I destroyed it in the process.
This hole is for the depth sounder. The two small holes accept bolts for the fairing block. The nice thing about steel is the holes are threaded.
Both holes needed to be enlarged. For the speed impeller I tapped in a piece of tapered square wood as far as it would go.
Here I cut the wood off. I used a hole saw that has a drill bit in the center. The drill bit goes in the wood and holds the saw centered while I drill through.
For the depth transducer I also had to enlarge the hole in the fairing block. I set the holesaw in the fairing block and started cutting. It acted as a guide for when the hole saw reached the steel.
The end result in both cases was a ring of steel.