This is my first post here, hoping you can provide some good advice.
My chart plotter died some time ago and the old transducer that was connected to it will not work anymore. I want to install a couple of standard Airmar transducers for depth and speed. They are about 51mm in diameter. Can anyone tell me the best and easiest and neatest way to make the holes required? I have tried using a diamond holes when I had to make a hole in the deck for the windlass cables, it would cost the concrete fine but struggled through the steel and had a big tendency to wander. Masonry bits go straight through no worries but are deflected by the steel. Drilling a ring of small holes around the perimeter would work but is not neat.
I am thinking they will need to be somewhere between 55 and 60 mm diameter and be sealed with thickened epoxy to protect the steel in the boat. I am wondering if I should fill the hole with epoxy then rebore them to the size needed for the transducers or whether I should try and find something the right diameter to plug the hole and get the epoxy around that. Standard sikaflex tubes are an almost perfect size for that. Another option would be to bore slightly oversize then just epoxy the outside part of the transducer into the hole, thereby sealing the hole and protecting the steel in one go.
All opinions and advice gratefully accepted.