Used the bag of water-time for the next step
I spent an hour or so with my Lowrance HDS5 and its sonar transducer yesterday. With the transducer in a plastic bag of water I did find a location that is easy to reach and gave an accurate reading of depth at 7.5 to 10 ft. I checked the depth with a weighted line over the side. So "permanent" installation is now in order, and I appreciate all the alternatives offered in this discussion. Lowrance stresses the importance of using the right epoxy-a hard, non-flexible bond-and specifies an EFI product. I like the idea of plumber's putty instead if it works as well as some of you have said-at least as an interim solution.
Thanks again for the input....