I had this exact problem last fall. My Datamarine depth sounder was heavily glassed into the hull in the space under the vee-berth, port side. I ended up using a Fein multipurpose tool saw and cut it off flush with the inside of the hull. The tube was made of bronze and nothing under the sun was going to get the inside nut to come loose so I could simply pop it out. Once it was cut off flush with the inside of the hull, I used a hole saw to cut a new hole through the hull right where the old transducer stub remained. The hole saw was the size of the new depth sounder tube...about 4.25 inches as I recall.
The hardest part of this whole operation was getting the multi-tool saw to cut through the bronze tube. It was a bugger. A friend loaned me his tool. Ironically, I just bought my own today from Home Depot. I bought the Bosch multi-tool and paid around $150.00. You can put a sander head as well as a bunch of other heads on it...including the saw blade head. Home Depot also makes it's own brand that has a bunch of attachments that can be clipped onto the head. It listed for $129.00.
Bob Rude
#352
Mmmmm
